The Collaborative International Dictionary of English v.0.48:

Yacca \Yac"ca\ (y[a^]k"k[.a]), n. (Bot.)
   A West Indian name for two large timber trees (Podocarpus
   coriaceus, and Podocarpus Purdicanus) of the Yew family.
   The wood, which is much used, is pale brownish with darker
   streaks.
   [1913 Webster]

WordNet (r) 3.0 (2006):

yacca
    n 1: West Indian evergreen with medium to long leaves [syn:
         yacca, yacca podocarp, Podocarpus coriaceus]