uncompromising.adjective
unwilling to grant concessions or negotiate; inflexible: took an uncompromising stance during the peace talks; displayed uncompromising honesty
uncompromisingly.adverb

ulterior.adjective
lying beyond what is evident, revealed, or avowed, especially being concealed intentionally so as to deceive (an ulterior motive); lying beyond or outside the area of immediate interest; occurring later; subsequent; on the other side
ulteriorly.adverb

upbraid, upbraided, upbraiding, upbraids.transitive verbs
to reprove sharply; to get after; reproach; scold; upbraid generally suggests a well founded reproach, as one leveled by an authority (upbraided him for not having worn his overcoat out in the cold)
upbraider.noun
upbraidingly.adverb

unduly.adverb
excessively; immoderately (unduly familiar with strangers)

unsubstantial.adjective
lacking material substance; insubstantial; lacking firmness or strength; flimsy; lacking basis in fact
unsubstantiality.noun
unsubstantially.adverb

underpin, underpinned, underpinning, underpins.transitive verbs
to give support or substance to; to support from below, as with props, girders, or masonry

unprecedented.adjective
having no previous example (unprecedented economic growth)
unprecedentedly.adverb

unctuous.adjective
characterized by affected, exaggerated, or insincere earnestness; smarmy; having the quality or characteristics of oil or ointment; slippery; containing or composed of oil or fat
unctuously.adverb
unctuousness or unctuosity.noun

unwary, unwarier, unwariest.adjectives
not alert to danger or deception
unwarily.adverb
unwariness.noun

unbecoming.adjective
not appropriate, attractive, or flattering (an unbecoming dress); not in accord with the standards implied by one's character or position (conduct unbecoming an officer of the company); improper
unbecomingly.adverb
unbecomingness.noun

unalienable.adjective
not to be separated, given away, or taken away; inalienable.(inalienable rights)

umbrage.noun
offense; resentment (took umbrage at their rudeness); something that affords shade; shadow or shad; a vague or indistinct indication; a hint of shadow or darkness; Note: umbrage is often followed by at (took umbrage at the comment; I imagine some people will take umbrage {=will be offended} when they hear the quote; example - I take umbrage at {=I am offended by} that remark)

unnerve, unnerved, unnerving, unnerves.transitive verbs
to deprive of fortitude, strength, or firmness of purpose; to make nervous or upset
unnervingly.adverb

uniform.adjective
always the same, as in character or degree; unvarying; conforming to one principle, standard, or rule; consistent; being the same as or consonant with another or others; unvaried in texture, color, or design; steady
uniform.noun
one form; a distinctive outfit intended to identify those who wear it as members of a specific group; one set of such an outfit. uniform, uniformed, uniforming, uniforms.transitive verbs
to make (something) uniform; to provide or dress with a uniform
uniformity.or.uniformness.noun
uniformly.adverb

unpremeditated.adjective
not planned or thought out in advance; extemporaneous
unpremeditatedly.adverb
compare premeditated

unstable, unstabler, unstablest.adjectives
tending strongly to change (unstable weather); lacking control of one's emotions; not constant; fluctuating.(unstable vital signs); fickle; characterized by unpredictable behavior; not firmly placed; unsteady (an unstable ladder)
unstableness.noun
unstably.adverb
Chemistry.-.decomposing.readily
Physics.-.decaying with relatively short lifetime; used of subatomic.particles; radioactive

usher.noun
one who is employed to escort people to their seats, as in a theater, church, or stadium.
usher, ushered, ushering, ushers.verbs
transitive verb use.to serve as an usher to; escort; to lead or conduct; gguide; to precede and introduce; inaugurate
intransitive verb use.to serve as an usher (ushered every Sunday at church)

unify, unified, unifying, unifies.transitive & intransitive verbs
to make into or become a unit; consolidate
unifiable.adjective
unification, unifier.nouns

unite, united, uniting, unites.verbs
transitive verb use.to bring together so as to form a whole; to combine (people) in interest, attitude, or action (love unites humanity); to join (a couple) in marriage; to cause to adhere; to join and act together in a common purpose or endeavor; join; o be or become bound together by adhesion

unity.noun, plural.unities
the state or quality of being one; singleness; the state or quality of being in accord; harmony; the combination or arrangement of parts into a whole; unification; a combination or union thus formed; singleness or constancy of purpose or action

undeceive, undeceived, undeceiving, undeceives.transitive verbs
to free from illusion or deception
undeceivable.adjective
undeceivably.adverb

union.noun
the act of uniting or the state of being united; a combination so formed, especially an alliance or confederation of people, parties for mutual interest or benefit; unity; a labor union; a student union
union.adjective