The Collaborative International Dictionary of English v.0.48:

Arecidae \Arecidae\ n.
   1. 1 one of four subclasses or superorder of Monocotyledones;
      comprises about 6400 species in 5 families of trees and
      shrubs and terrestrial herbs and a few free-floating
      aquatics including: Palmae; Araceae; Pandanaceae: and
      Lemnaceae.

   Syn: subclass Arecidae
        [WordNet 1.5] Arecoline

WordNet (r) 3.0 (2006):

Arecidae
    n 1: one of four subclasses or superorder of Monocotyledones;
         comprises about 6400 species in 5 families of trees and
         shrubs and terrestrial herbs and a few free-floating
         aquatics including: Palmae; Araceae; Pandanaceae and
         Lemnaceae [syn: Arecidae, subclass Arecidae]