| Term | Definition |
| unison | harmony; agreement |
| universal | broad; general; effective everywhere or in all cases |
| unkempt | untidy; sloppy |
| unmindful | unaware |
| unmitigated | absolute; not lessened |
| unobtrusive | inconspicuous; not noticeable |
| unruly | not manageable; disorderly |
| unsavory | unpleasant to taste or smell |
| unscathed | unharmed; uninjured |
| unseemly | not in good taste |
| untenable | unable to be defended or upheld |
| unwieldy | hard to manage because of size or weight |
| unwitting | unintentional; unaware |
| upbraid | to scold; to find fault with |
| uproarious | loud; outrageously funny |
| urbane | refined; suave; citified |
| urchin | a mischievous child |
| ursine | like a bear |
| usurp | to seize illegally |
| usury | excessive amount of money charged as interest |
| utilitarian | useful; practical |
| utopian | perfect; ideal |
| uxorious | overly fond of one's wife |