ubiquitous - existing or being everywhere, esp. at the same time; omnipresent: ubiquitous fog; ubiquitous little ants. 
ulterior - being beyond what is seen or avowed; intentionally kept concealed: ulterior motives. coming at a subsequent time or stage; future; further: ulterior action. lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed); "subterranean motives for murder"; "looked too closely for an ulterior purpose in all knowledge"- Bertrand Russell
ultimate - ADj   furthest or highest in degree or order; utmost or extreme; "the ultimate achievement"; "the ultimate question"; "man's ultimate destiny"; "the ultimate insult"; "one's ultimate goal in life last; furthest or farthest; ending a process or series: the ultimate point in a journey; the ultimate style in hats. maximum; decisive; conclusive: the ultimate authority; the ultimate weapon. 
ultimatum -N a final, uncompromising demand or set of terms issued by a party to a dispute, the rejection of which may lead to a severance of relations or to the use of force. 
ulcer - a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue
umbrage - a feeling of anger caused by being offended; "he took offence at my question" offense; annoyance; displeasure: to feel umbrage at a social snub; to give umbrage to someone; to take umbrage at someone's rudeness. 
unaccountable -impossible to account for; unexplained; inexplicable: The boat has an unaccountable tendency to yaw.  not to be accounted for or explained; "perceptible only as unaccountable influences that hinder progress"; "an unexplainable fear"
unanimity -the state or quality of being unanimous; a consensus or undivided opinion: The unanimity of the delegates was obvious on the first ballot.  Unanimity among politicians is rare. 
 unanimous -  N in complete agreement; "a unanimous decision"
unassailable - able to withstand attack; "an impregnable fortress"; "fortunaccustomed - not habituated to; unfamiliar with; "unaccustomed to wearing suits" to be unaccustomed to hardships. unusual; unfamiliar: A brief after-dinner speech is an unaccustomed pleasure. 
unaware - not aware or conscious; unconscious: to be unaware of any change. (often followed by `of') not aware; "seemed unaware of the scrutiny"; "unaware of the danger they were in"; "unaware of the newborn hope"; "the most unaware person I've known"
unbridled - not restrained or controlled; "unbridled rage"; "an unchecked temper"; "ungoverned rage"
unbiased - characterized by a lack of partiality; "a properly indifferent jury"; "an unbiased account of her family problems"
uncanny - having or seeming to have a supernatural or inexplicable basis; beyond the ordinary or normal; extraordinary: uncanny accuracy; an uncanny knack of foreseeing troublesuggesting the operation of supernatural influences; "an eldritch screech"; "the three weird sisters"; "stumps...had uncanny shapes as of monstrous creatures"- John Galsworthy; "an unearthly light"; "he could hear the unearthly scream of some curlew piercing the din"- Henry Kingsley
unconscionable - not in accordance with what is just or reasonable: unconscionable behavior. lacking a conscience; "a conscienceless villain"; "brash, unprincipled, and conscienceless"; "an unconscionable liar"
uncouth -ADj  awkward, clumsy, or unmannerly: uncouth behavior; an uncouth relative who embarrasses the family.  lacking refinement or cultivation or taste; "he had coarse manners but a first-rate mind"; "behavior that branded him as common"; "an untutored and uncouth human being"; "an uncouth soldier--a real tough guy"; "appealing to the vulgar taste for violence"; "the vulgar display of the newly rich
uncommon - ADj   not common; unusual; rare: an uncommon word. unusual in amount or degree; above the ordinary: an uncommon amount of mail. not common or ordinarily encountered; unusually great in amount or remarkable in character or kind; "uncommon birds"; "frost and floods are uncommon during these months"; "doing an uncommon amount of business"; "an uncommon liking for money"; "he owed his greatest debt to his mother's uncommon character and ability"
uncompromising - ADj not admitting of compromise or adjustment of differences; making no concessions; inaccessible to flexible bargaining; unyielding: an uncompromising attitude.  not making concessions; "took an uncompromising stance in the peace talks"; "uncompromising honesty" You should not adopt such an uncompromising attitude. 
unconcealed - not concealed or hidden; "her unconcealed hostility poisoned the atmosphere"; "watched with unconcealed curiosity"
unconcern -Nlack of interest or anxiety: He received the news of his failure with apparent unconcern. 
unconditional - not conditional; "unconditional surrender"
unctuous - unpleasantly and excessively suave or ingratiating in manner or speech; "buttery praise"; "gave him a fulsome introduction"; "an oily sycophantic press agent"; "oleaginous hypocrisy"; "smarmy self-importance"; "the unctuous Uriah Heep"
underlying - in the nature of something though not readily apparent; "shortcomings inherent in our approach"; "an underlying meaning"
undaunted - resolutely courageous; "undaunted in the face of death"
undecided - not brought to a conclusion; subject to further thought; "an open question"; "our position on this bill is still undecided"; "our lawsuit is still undetermined
undeniable -incapable of being denied or disputed: undeniable evidence of arson. 
undergo - V  to be subjected to; experience; pass through: to undergo surgery.  of mental or physical states or experiences; "get an idea"; "experience vertigo"; "get nauseous"; "undergo a strange sensation"; "The chemical undergoes a sudden change"; "The fluid undergoes shear"; "receive injuries"; "have a feeling  go or live through; "We had many trials to go through"; "he saw action in Viet Nam" to go through (a process) The car is undergoing tests/repairs; She has been undergoing medical treatment. 
undermine - V   To weaken by wearing away a base or foundation: Water has undermined the stone foundations. To weaken, injure, or impair, often by degrees or imperceptibly; sap: Late hours can undermine one's health. 
underscore -V  to stress; emphasize: The recent tragedy underscores the danger of disregarding safety rules. 
undulate -V to move with a sinuous or wavelike motion; display a smooth rising-and-falling or side-to-side alternation of movement: The flag undulates in the breeze. 
unearthly - ADj seeming not to belong to this earth or world: unearthly beauty.  outrageous or unreasonableHe telephoned at the unearthly (= very early) hour of 6.30 a.m. 
unequivocal - not equivocal; unambiguous; clear; having only one possible meaning or interpretation: an unequivocal indication of assent; unequivocal proof. admitting of no doubt or misunderstanding; having only one meaning or interpretation and leading to only one conclusion; "unequivocal evidence"; "took an unequivocal position"; "an unequivocal success"; "an unequivocal promise"; "an unequivocal (or univocal) statement" The cosigner of a note gives unequivocal assurance that it will be paid when due. 
unerring - ADJ   not erring; not going astray or missing the mark: The captain set an unerring course for home.  undeviatingly accurate throughout; not containing any error or flaw: She gave an unerring recital of the day's events. 
unexceptionable - completely acceptable; not open to exception or reproach; "two unexceptionable witnesses"; "a judge's ethics should be unexceptionable" an unexceptionable record of achievement. 
uneasy - ADJ  lacking a sense of security or affording no ease or reassurance; "farmers were uneasy until rain finally came"; "uneasy about his health"; "gave an uneasy laugh"; "uneasy lies the head that wears the crown"; "an uneasy coalition government"; "an uneasy calm"; "an uneasy silence fell on the group"
unfaltering - ADJ   marked by firm determination or resolution; not shakable; "firm convictions"; "a firm mouth"; "steadfast resolve"; "a man of unbendable perseverence"; "unwavering loyalty
unfeigned - ADJ   not pretended; sincerely felt or expressed; "genuine emotion"; "her interest in people was unfeigned"; "true grief"
unfledged - young and inexperienced; "a fledgling enterprise"; "a fledgling skier"; "an unfledged lawyer"
ungainly -  أخْرَق، فَظ، غَيْر رَشيق  not graceful; awkward; unwieldy; clumsy: an ungainly child; an ungainly prose style. lacking grace in movement or posture; "a gawky lad with long ungainly legs"; "clumsy fingers"; "what an ungainly creature a giraffe is"; "heaved his unwieldy figure out of his chair
unguent - semisolid preparation (usually containing a medicine) applied externally as a remedy or for soothing an irritation
uniformity - N the state or quality of being uniform; overall sameness, homogeneity, or regularity: uniformity of style. The houses in the street had no uniformity of appearance. 
unify -V  become one; "Germany unified officially in 1990"; "Will the two Koreas unify?"
unilateral - relating to, occurring on, or involving one side only: unilateral development; a unilateral approach. involving only one part or side; "unilateral paralysis"; "a unilateral decision"Of, on, relating to, involving, or affecting only one side: "a unilateral advantage in defense"  undertaken or done by or on behalf of one side, party, or faction only; not mutual: a unilateral decision; unilateral disarmament. 
unimpeachable - beyond doubt or reproach; "an unimpeachable source"free of guilt; not subject to blame; "has lived a blameless life"; unimpeachable behavior. "of irreproachable character"; "an unimpeachable reputation"
unimportant - not important; "a relatively unimportant feature of the system"; "the question seems unimportant"
uninhibited - ADj not inhibited or restrained; "uninhibited exuberance" an uninhibited discussion of the causes of divorce. 
unique -ADJ  existing as the only one or as the sole example; single; solitary in type or characteristics: a unique copy of an ancient manuscript.  having no like or equal; unparalleled; incomparable: Bach was unique in his handling of counterpoint. limited in occurrence to a given class, situation, or area: a species unique to Australia.  radically distinctive and without equal; "he is alone in the field of microbiology"; "this theory is altogether alone in its penetration of the problem"; "Bach was unique in his handling of counterpoint"; "craftsmen whose skill is unequaled"; "unparalleled athletic ability"; "a breakdown of law unparalleled in our history"
unison - N  corresponding exactly; "marching in unison"
universal - ADJ  of, pertaining to, or characteristic of all or the whole: universal experience. applicable everywhere or in all cases; general: a universal cure.    affecting, concerning, or involving all: universal military service. Of, relating to, extending to, or affecting the entire world or all within the world; worldwide: "This discovery of literature has as yet only partially penetrated the universal consciousness" Ellen Key.
unkempt - not neatly combed; "wild unkempt hair"uncared-for or neglected; disheveled; messy: unkempt clothes; an unkempt lawn. 
unmitigated - not diminished or moderated in intensity or severity; sometimes used as an intensifier; "unmitigated suffering"; "an unmitigated horror"; "an unmitigated lie"unmitigated suffering. 
unmixed - not mixed with extraneous elements; "plain water"; "sheer wine"; "not an unmixed blessing"Free from other elements; pure: unmixed pleasure; an unmixed blessing
unobtrusive - not obtrusive or undesirably noticeable; "a quiet, unobtrusive life of self-denial"She is quiet and unobtrusive. 
unprecedented - having no precedent; novel; "an unprecedented expansion in population and industry" an unprecedented event. Such an action by a prime minister is unprecedented. 
unprepossessing -ADjNot overtly impressive; unremarkable; nondescript: an unprepossessing little hotel. 
unravel -V to free from complication or difficulty; make plain or clear; solve: to unravel a situation; to unravel a mystery. 
unrequited -ADJ not returned or reciprocated: unrequited love. 
unreserved -ADj  not restricted; without reservation; full; entire; unqualified: unreserved approval. free from reserve; frank; open: unreserved behavior  She had a cheerful, unreserved nature. 
unrestricted - free of restrictions on conduct; "I had unrestricted access"
unruly -ADJ not submissive or conforming to rule; ungovernable; turbulent; intractable; refractory; lawless: an unruly class; an unruly wilderness. noisy and lacking in restraint or discipline; "a boisterous crowd"; "a social gathering that became rambunctious and out of hand"; "a robustious group of teenagers"; "beneath the rumbustious surface of his paintings is sympathy for the vulnerability of ordinary human beings"; "an unruly class"unruly teenagers/behaviour 
unreasonable -not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational: an unreasonable person. 
unrest - a state of agitation or turbulent change or development; "the political ferment produced a new leadership"; "social unrest   "political unrest 
unsavory -ADJ  morally offensive; "an unsavory reputation"; "an unsavory scandal"  Distasteful or disagreeable: an unsavory task.
unscathed - not scathed; unharmed; uninjured: She survived the accident unscathed. 
unseemly -  ADJ  not seemly; not in keeping with established standards of taste or proper form; unbecoming or indecorous in appearance, speech, conduct, etc.: an unseemly act; unseemly behavior.  not in keeping with accepted standards of what is right or proper in polite society; "was buried with indecent haste"; "indecorous behavior"; "language unbecoming to a lady"; "unseemly to use profanity"; "moved to curb their untoward ribaldry"
unselective - not selective or discriminating; "unselective in her reading habits; her choices seemed completely random
unsightly - unpleasant to look at; "unsightly billboards"an unsightly wound; unsightly disorder. Those new buildings are very unsightly. 
unsullied - spotlessly clean and fresh; "the unsullied snow of mountains"; "the unsullied splender of eternal youth"- of reputation; "his unsullied name"; "an untarnished reputation"
unsound - not in good condition; damaged or decayed; "an unsound foundation not well-founded or valid; fallacious: an unsound argument. 
unsparing - very generous; "distributed gifts with a lavish hand"; "the critics were lavish in their praise"; "a munificent gift"; "his father gave him a half-dollar and his mother a quarter and he thought them munificent"; "prodigal praise"; "unsparing generosity"; "his unstinted devotion"; "called for unstinting aid to Britain"
unstable - ADJ lacking stability or fixity or firmness; "unstable political conditions"; "the tower proved to be unstable in the high wind"; "an unstable world economy"
unsteady - subject to change or variation especially in behavior; "her unsteady walk"; "his hand was unsteady as he poured the wine"; "an unsteady voice"
unseat -V  remove from political office; "The Republicans are trying to unseat the liberal Democrat"
untenable -Being such that defense or maintenance is impossible: an untenable position. 
untoward - ADJ  unfavorable or unfortunate: Untoward circumstances forced him into bankruptcy.  not in keeping with accepted standards of what is right or proper in polite society; "was buried with indecent haste"; "indecorous behavior"; "language unbecoming to a lady"; "unseemly to use profanity"; "moved to curb their untoward ribaldry
unwarranted - without a basis in reason or fact; "baseless gossip"; "the allegations proved groundless"; "idle fears"; "unfounded suspicions"; "unwarranted jealousy"
unwell - somewhat ill or prone to illness; "my poor ailing grandmother"; "feeling a bit indisposed today"; "you look a little peaked"; "feeling poorly"; "a sickly child"; "is unwell and can't come to work"
unwieldy - difficult to use or handle or manage because of size or weight or shape; "we set about towing the unwieldy structure into the shelter"; "almost dropped the unwieldy parcel
unwitting - not intentional; "an unintended slight"; "an unintentional pun"; "the offense was unintentional"; "an unwitting mistake may be overlooked"
unwonted - out of the ordinary; "an unwonted softness in her face"
upbraid -V to find fault with or reproach severely; censure: The military tribunal upbraided the soldier for his cowardice.  express criticism towards; "The president reproached the general for his irresponsible behavior"
uproarious - marked by or causing boisterous merriment or convulsive laughter; "hilarious broad comedy"; "a screaming farce"; "uproarious stories
upshot - a phenomenon that follows and is caused by some previous phenomenon; "the magnetic effect was greater when the rod was lengthwise"; "his decision had depressing consequences for business"; "he acted very wise after the event The upshot of the disagreement was a new bylaw. What was the final upshot of that affair? 
urbane -ADJ  showing a high degree of refinement and the assurance that comes from wide social experience; "his polished manner"; "maintained an urbane tone in his letters" having the polish and suavity regarded as characteristic of sophisticated social life in major cities: an urbane manner. 
urchin -N  a mischievous, usually dirty or ragged, child, especially a boy He was chased by a crowd of urchins. 
usurp -V  seize and take control without authority and possibly with force; take as one's right or possession;The pretender tried to usurp the throne.The king's uncle tried to usurp the throne; I shall not allow him to usurp my authority.  "He assumed to himself the right to fill all positions in the town"; "he usurped my rights"; "She seized control of the throne after her husband died"
usury - an exorbitant or unlawful rate of interest
utopia - المَدينَةُ الفاضِلَهideally perfect state; especially in its social and political and moral aspects
utilize - put into service; make work or employ (something) for a particular purpose or for its inherent or natural purpose; "use your head!"; "we only use Spanish at home"; "I can't make use of this tool"; "Apply a magnetic field here"; "This thinking was applied to many projects"; "How do you utilize this tool?"; "I apply this rule to get good results"; "use the plastic bags to store the food"; "He doesn't know how to use a computer"
utmost -N of the greatest or highest degree, quantity, or the like; greatest: Take the utmost care! of the utmost importance. being at the farthest point or extremity; farthest: the utmost reef of the island. 
utensil -N any of the instruments or vessels commonly used in a kitchen, dairy, etc.: eating utensils;: pots and pans and other kitchen utensils  baking utensils. any instrument, vessel, or tool serving a useful purpose: smoking utensils; fishing utensils; farming utensils. 

Synonyms: unruly, intractable, refractory, recalcitrant, headstrong, wayward
These adjectives mean resistant or marked by resistance to control. Unruly implies failure to submit to rule or discipline: unruly behavior in class.
Intractable and refractory refer to what is obstinate and difficult to manage or control: "the intractable ferocity of his captive" Edgar Allan Poe. "The idea of ecclesiastical authority ... woke all the refractory nerves of opposition inherited from five generations of Puritans" Harriet Beecher Stowe.
One that is recalcitrant rebels against authority: arrested the recalcitrant protestors.
Headstrong describe one obstinately bent on having his or her own way: The headstrong senator ignored his constituency.
One who is wayward willfully and often perversely departs from what is desired, advised, expected, or required: "a lively child, who had been spoilt and indulged, and therefore was sometimes wayward" Charlotte Brontë.