The Collaborative International Dictionary of English v.0.48:

Fagaceae \Fagaceae\ prop. n.
   a natural family of chiefly monoecious trees and shrubs,
   including beeches, chestnuts, and oaks; it includes the
   genera Castanea; Castanopsis; Chrysolepis; Fagus;
   Lithocarpus; Nothofagus; and Quercus.

   Syn: family Fagaceae, beech family.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Fagaceae
    n 1: chiefly monoecious trees and shrubs: beeches; chestnuts;
         oaks; genera Castanea, Castanopsis, Chrysolepis, Fagus,
         Lithocarpus, Nothofagus, Quercus [syn: Fagaceae, family
         Fagaceae, beech family]