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 catechu
    n 1: southeastern Asian palm bearing betel nuts (scarlet or
         orange single-seeded fruit with a fibrous husk) [syn:
         betel palm, Areca catechu]