| AUTOGIROS | • autogiros n. Plural of autogiro. • AUTOGIRO n. (Spanish) a rotating wing aircraft, also AUTOGYRO. |
| OLINGUITO | • olinguito n. Bassaricyon neblina, a raccoon-like procyonid native to the Andean forests of Colombia and Ecuador. • OLINGUITO n. (Spanish) a small animal related to the olingo, living in the forests of Colombia and Ecuador. |
| OUTBOXING | • outboxing v. Present participle of outbox. • OUTBOX v. to surpass in boxing. |
| OUTFOXING | • outfoxing v. Present participle of outfox. • OUTFOX v. to outwit. |
| OUTGOINGS | • outgoings n. Plural of outgoing. • OUTGOING n. a departure; an expenditure. |
| OUTLOVING | • outloving v. Present participle of outlove. • OUTLOVE v. to surpass in loving. |
| OUTMODING | • outmoding v. Present participle of outmode. • outmoding n. The act or process of something becoming outmoded. • OUTMODE v. to put out of fashion. |
| OUTMOVING | • outmoving v. Present participle of outmove. • OUTMOVE v. to move faster than. |
| OUTROWING | • outrowing v. Present participle of outrow. • OUTROW v. to surpass in rowing. |
| OUTVOTING | • outvoting v. Present participle of outvote. • OUTVOTE v. to defeat by a majority of votes. |
| TRIGONOUS | • trigonous adj. Trigonal. • TRIGONOUS adj. having a triangular cross-section. |
| UFOLOGIST | • ufologist n. A person who studies UFOs. • UFOLOGIST n. one interested in ufos. |
| UNBOOTING | • unbooting v. Present participle of unboot. • UNBOOT v. to take off the boots. |
| UNROOTING | • unrooting v. Present participle of unroot. • UNROOT v. to tear up by the roots. |
| UPROOTING | • uprooting v. Present participle of uproot. • uprooting n. A tearing up. • UPROOTING n. the act of uprooting. |
| UROLOGIST | • urologist n. (Medicine) A doctor of urology. • UROLOGIST n. one versed in urology, the study of urine. |