The Collaborative International Dictionary of English v.0.48:

Betulaceae \Betulaceae\ n.
   1. a natural family of monoecious trees and shrubs, including
      the genera Betula; Alnus; Carpinus; Corylus;
      Ostrya; and Ostryopsis.

   Syn: family Betulaceae, birch family.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Betulaceae
    n 1: monoecious trees and shrubs (including the genera Betula
         and Alnus and Carpinus and Corylus and Ostrya and
         Ostryopsis) [syn: Betulaceae, family Betulaceae, birch
         family]