The Collaborative International Dictionary of English v.0.48:

Areca \A*re"ca\, n. [Canarese adiki: cf. Pg. & Sp. areca.]
   (Bot.)
   A genus of palms, one species of which (Areca catechu)
   produces the areca nut, or betel nut, which is chewed in
   India and Southeast Asia with the leaf of the Piper Betle
   and lime.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

areca
    n 1: any of several tall tropical palms native to southeastern
         Asia having egg-shaped nuts