U

ubiquitous adj. Being present everywhere.
ulterior adj. Not so pertinent as something else to the matter spoken of.
ultimatum n. A final statement or proposal, as concerning terms or conditions.
ultramundane adj. Pertaining to supernatural things or to another life.
ultramontane adj. Beyond the mountains, especially beyond the Alps (that is, on their Italian side).
umbrage n. A sense of injury.
unaccountable adj. Inexplicable.
unavoidable adj. Inevitable.
unbecoming adj. Unsuited to the wearer, place, or surroundings.
unbiased adj. Impartial, as judgment.
unbridled adj. Being without restraint.
unctuous adj. Oily.
underling n. A subordinate.
undermine v. To subvert in an underhand way.
underrate v. To undervalue.
understate v. To fail to put strongly enough, as a case.
undulate v. To move like a wave or in waves.
undulous adj. Resembling waves.
ungainly adj. Clumsy.
unguent n. Any ointment or lubricant for local application.
unicellular adj. Consisting of a single cell.
univalence n. Monovalency.
unison n. A condition of perfect agreement and accord.
unisonant adj. Being in a condition of perfect agreement and accord.
unsettle v. To put into confusion.
untoward adj. Causing annoyance or hindrance.
unwieldy adj. Moved or managed with difficulty, as from great size or awkward shape.
unyoke v. To separate.
upbraid v. To reproach as deserving blame.
upheaval n. Overthrow or violent disturbance of established order or condition.
upheave v. To raise or lift with effort.
uppermost adj. First in order of precedence.
uproarious adj. Noisy.
uproot v. To eradicate.
upturn v. To throw into confusion.
urchin n. A roguish, mischievous boy.
usurious adj. Taking unlawful or exorbitant interest on money loaned.
usurp v. To take possession of by force.
usury n. The demanding for the use of money as a loan, a rate of interest beyond what is allowed by law.
utilitarianism n. The ethical doctrine that actions are right because they are useful or of beneficial tendency.
utmost n. The greatest possible extent.