The Collaborative International Dictionary of English v.0.48:

cacao \ca*ca"o\, n. [Sp., fr. Mex. kakahuatl. Cf. Cocoa,
   Chocolate] (Bot.)
   A small evergreen tree (Theobroma Cacao) of South America
   and the West Indies. Its fruit contains an edible pulp,
   inclosing seeds about the size of an almond, from which
   cocoa, chocolate, and broma are prepared.
   [1913 Webster] Cachaemia

WordNet (r) 3.0 (2006):

cacao
    n 1: tropical American tree producing cacao beans [syn: cacao,
         cacao tree, chocolate tree, Theobroma cacao]