(literally) With a single blow, effort, or act. / (figuratively, by extension) At once, immediately; in an instant.

plural of one-upmanship

In a watchful state; alert; vigilant.

(sports) a type of elimination playoff series that is a single-game series, to decide who wins the playoff round

(now chiefly UK) Penultimate, next to last, immediately preceding the end of a sequence, list, etc.

simple past tense and past participle of one-up

plural of one-up

Third-person singular simple present indicative form of one-up

present participle of one-up

Used to emphasize the truth of a characterization