The Collaborative International Dictionary of English v.0.48:

Opuntia \O*pun"ti*a\, prop. n. [NL.] (Bot.)
   A genus of cactaceous plants; the prickly pear, or Indian
   fig.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Opuntia
    n 1: large genus of cactuses native to America: prickly pears
         [syn: Opuntia, genus Opuntia]