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 ]