Ace \Ace\, n.; pl. {Aces}. [OE. as, F. as, fr. L. as, assis, unity, copper coin, the unit of coinage. Cf. {As}.] 1. A unit; a single point or spot on a card or die; the card or die so marked; as, the ace of diamonds. 2. Hence: A very small quantity or degree; a particle; an atom; a jot. I 'll not wag an ace further. --Dryden. {To bate an ace}, to make the least abatement. [Obs.] {Within an ace of}, very near; on the point of. --W. Irving.