- unsmiling (adj.)
- 1826, from un- (1) "not" + present participle of smile (v.).
- unsociable (adj.)
- c.1600, from un- (1) "not" + sociable.
- unsolicited (adj.)
- 1580s, from un- (1) "not" + past participle of solicit.
- unsophisticated (adj.)
- 1620s, "unmixed," from un- (1) "not" + sophisticated. Meaning "ingenuous, natural, inexperienced" is recorded from 1660s.
- unsought
- early 13c., from un- (1) "not" + past participle of seek. Cf. Middle Dutch ongesocht, Dutch ongezocht, Middle High German ungesuochet, German ungesucht.
- unsound (adj.)
- early 14c., of persons, "diseased, wounded," from un- (1) "not" + sound (adj.). Cf. Middle Low German unsund, Middle Dutch ongesont, German ungesund. Meaning "morally corrupt" is recorded from c.1300; that of "not mentally healthy" is from 1540s. Sense of "not based on reasoning or fact" is attested from 1590s.
- unsparing (adj.)
- "showing no mercy," 1580s, from un- (1) "not" + sparing (see spare (v.)). Related: Unsparingly.
- unspeakable (adj.)
- c.1400, "inexpressible," from un- (1) "not" + speakable (see speak). Meaning "indescribably bad or wicked" is recorded from 1831. Related: Unspeakably.
- unspoiled (adj.)
- c.1500, "not plundered," from un- (1) "not" + past participle of spoil (v.). Meaning "not deteriorated" is attested from 1732.
- unspoken (adj.)
- late 14c., from un- (1) "not" + past participle of speak. Cf. Middle Dutch ongesproken, Middle Low German ungesproken.
- unsportsmanlike (adj.)
- 1754, from un- (1) "not" + sportsmanlike (see sport (n.)). Unsporting is attested from 1859.
- unstable (adj.)
- early 13c., "apt to move," from un- (1) "not" + stable (adj.). Cf. Middle High German unstabel. Meaning "liable to fall" is recorded from c.1300; sense of "fickle" is attested from late 13c. An Old English word for this was feallendlic, which might have become *fally.
- unsteady (adj.)
- 1590s, from un- (1) "not" + steady (adj.). Cf. Old Frisian unstadich, German unstätig, Middle Dutch onstadich.
- unstinted (adj.)
- late 15c., from un- (1) "not" + past participle of stint (v.).
- unstinting (adj.)
- late 14c., "unceasing," from un- (1) "not" + present participle of stint (v.). Meaning "lavish" attested by 1845.
- unstoppable (adj.)
- 1836; see un- (1) "not" + stop (v.) + -able.
- unstrung (adj.)
- 1590s, "with strings relaxed" (of a harp, etc.), from un- (1) "not" + past participle of string (v.). Transferred sense of "weakened, unnerved" is recorded from 1690s.
- unsubscribe (v.)
- 1570s (implied in unsubscribed), from un- (2) "reverse of" + subscribe. Related: unsubscribing.
- unsubsidized (adj.)
- 1756, from un- (1) "not" + past participle of subsidize.
- unsubstantial (adj.)
- mid-15c., from un- (1) "not" + substantial.
- unsubstantiated (adj.)
- 1775, from un- (1) "not" + past participle of substantiate (v.).
- unsuccessful (adj.)
- 1610s, from un- (1) "not" + successful. Related: Unsuccessfully.
- unsuitable (adj.)
- 1590s, from un- (1) "not" + suitable. Related: Unsuitably; unsuitability.
- unsullied (adj.)
- 1580s, from un- (1) "not" + past participle of sully.
- unsung (adj.)
- early 15c., "not uttered in a song," from un- (1) "not" + past participle of sing. Cf. German ungesungen. Meaning "not celebrated" is recorded from 1660s.
- unsupervised (adj.)
- 1899, from un- (1) "not" + past participle of supervise.
- unsure (adj.)
- c.1400, "not safe against attack," also "lacking certainty," from un- (1) "not" + sure (adj.).
- unsurmountable (adj.)
- 1701, from un- (1) "not" + surmountable (see surmount).
- unsurpassable (adj.)
- 1610s, from un- (1) "not" + surpassable (see surpass).
- unsurpassed (adj.)
- 1775, from un- (1) "not" + past participle of surpass.
- unsuspected (adj.)
- 1520s, from un- (1) "not" + past participle of suspect (v.).
- unsuspecting (adj.)
- 1590s, from un- (1) "not" + present participle of suspect (v.).
- unsustainable (adj.)
- 1670s, from un- (1) "not" + sustainable.
- unswerving (adj.)
- 1690s, from un- (1) "not" + present participle of swerve (v.).
- unsympathetic (adj.)
- 1823, from un- (1) "not" + sympathetic.
- unsystematic (adj.)
- 1770, from un- (1) "not" + systematic.
- untainted (adj.)
- 1580s, in the moral sense; c.1600 in the physical sense; from un- (1) "not" + past participle of taint (v.).
- untamed (adj.)
- mid-14c., from un- (1) "not" + past participle of tame (v.). Cf. Old Norse utamdr, Old High German ungizamot.
- untangible (adj.)
- 1775, from un- (1) "not" + tangible.
- untangle (v.)
- 1540s, from un- (2) + tangle. Related: Untangled; untangling.
- untapped (adj.)
- 1775, from un- (1) "not" + past participle of tap (v.). Figurative use from c.1890.
- untempered (adj.)
- 1570s, from un- (1) "not" + past participle of temper (v.). Cf. Middle Dutch ongetempert, Middle High German ungetempert.
- untenable (adj.)
- 1640s, "incapable of being held against attack," from un- (1) "not" + past participle of tenable. Figurative sense is recorded from 1690s.
- untenanted (adj.)
- 1670s, from un- (1) "not" + tenanted (see tenant).
- untethered (adj.)
- 1775, from un- (1) "not" + past participle of tether (v.).
- unthaw (v.)
- 1590s, from un- (2) "opposite of" + thaw (v.). Related: Unthawed; unthawing.
- unthinkable (adj.)
- early 15c., "too large to be conceived, unimaginable," from un- (1) "not" + thinkable (see think). Meaning "incapable of being framed by thought" is recorded from mid-15c.
- unthinking (adj.)
- "unreflecting," 1670s, from un- + present participle of think.
- unthrifty (adj.)
- late 14c., from un- (1) "not" + thrifty.
- untidy (adj.)
- early 13c., "untimely, unseasonable, unsuitable," from un- (1) "not" + tidy (adj.). Cf. West Frisian ontidich, Middle Dutch ontidich, Dutch ontijdig, Old High German unzitich, German unzeitig, Norwegian utidig "untimely, unseasonable, unfavorable." Meaning "poorly cared for, not neat" is recorded from mid-14c.