The Collaborative International Dictionary of English v.0.48:

Trey \Trey\, n. [OF. treis three, F. trois, L. tres. See
   Three, and cf. Tray-trip.]
   Three, at cards, dice, or dominoes; a card, die, or domino of
   three spots or pips.
   [1913 Webster]

         Seven is my chance and thine is cinq and trey.
                                                  --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trey
    n 1: the cardinal number that is the sum of one and one and one
         [syn: three, 3, III, trio, threesome, tierce,
         leash, troika, triad, trine, trinity, ternary,
         ternion, triplet, tercet, terzetto, trey, deuce-
         ace]
    2: one of four playing cards in a deck having three pips [syn:
       trey, three]