n. & adj.
n. 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. 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.
[ ME f. OF f. L as unity, AS(2) ]