The Collaborative International Dictionary of English v.0.48:

Dicotyledonae \Dicotyledonae\ n. (Bot.)
   a class of plants comprising those seed plants that produce
   an embryo with two cotyledons and net-veined leaves; divided
   into six (not always well distinguished) subclasses (or
   superorders): Magnoliidae and Hamamelidae (considered
   primitive); Caryophyllidae (an early and distinctive
   offshoot); and three more or less advanced groups:
   Dilleniidae; Rosidae; Asteridae.

   Syn: Dicotyledones, class Dicotyledones, class Dicotyledonae,
        Magnoliopsida, class Magnoliopsida.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Rosidae
    n 1: a group of trees and shrubs and herbs mostly with
         polypetalous flowers; contains 108 families including
         Rosaceae; Crassulaceae; Myrtaceae; Melastomaceae;
         Euphorbiaceae; Umbelliferae [syn: Rosidae, subclass
         Rosidae]