The Collaborative International Dictionary of English v.0.48:

Truffle \Truf"fle\ (?; 277), n. [OF. trufle, F. truffe; akin to
   Sp. trufa, tartufo; of uncertain origin; perhaps from L.
   tuber a tumor, knob, truffle. Cf. Tuber, Trifle.]
   Any one of several kinds of roundish, subterranean fungi,
   usually of a blackish color. The French truffle (Tuber
   melanosporum) and the English truffle (Tuber aestivum) are
   much esteemed as articles of food.
   [1913 Webster]

   Truffle worm (Zool.), the larva of a fly of the genus
      Leiodes, injurious to truffles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

truffle
    n 1: any of various highly prized edible subterranean fungi of
         the genus Tuber; grow naturally in southwestern Europe
         [syn: truffle, earthnut, earth-ball]
    2: edible subterranean fungus of the genus Tuber [syn:
       truffle, earthnut]
    3: creamy chocolate candy [syn: truffle, chocolate truffle]