n. & adj.
1. a a playing-card, domino, etc., with a single spot and generally having the value 'one' or in card-games the highest value in each suit. b a single spot on a playing-card etc.
2 a a person who excels in some activity. b Aeron. a pilot who has shot down many enemy aircraft.
3 a (in lawn tennis) a stroke (esp. a service) too good for the opponent to return. b a point scored in this way.
--adj. sl. excellent.
Phrases and idioms:
ace up one's sleeve (US in the hole) something effective kept in reserve. play one's ace use one's best resource. within an ace of on the verge of.
Etymology: ME f. OF f. L as unity, AS(2)