Definition of: ace

(ās) noun
1. A single spot, as on a playing card or die; a card or side of a die so marked.
2. A very small amount, distance, or degree; a unit; particle.
3. Something excellent or first-rate; hence, one who excels in any field.
4. A military aviator who has destroyed five or more enemy aircraft.
5. In tennis and similar games, a point won by a single stroke, as upon the service.
—within an ace Within a hair's breadth; on the very point or verge.
—v.t. aced (āst), ac·ing
1. To score a point against in a single stroke, as upon the service in tennis.
2. Slang To get the better of, as by a timely move or act. [<OF as <L as unity, unit]