The Collaborative International Dictionary of English v.0.48:

Magnoliidae \Magnoliidae\ n.
   a group of families of trees and shrubs and herbs having
   well-developed perianths and apocarpous ovaries and generally
   regarded as the most primitive extant flowering plants;
   contains 36 families including Magnoliaceae and
   Ranunculaceae; sometimes classified as a superorder.

   Syn: subclass Magnoliidae, ranalian complex.
        [WordNet 1.5]

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):

Magnoliidae
    n 1: a group of families of trees and shrubs and herbs having
         well-developed perianths and apocarpous ovaries and
         generally regarded as the most primitive extant flowering
         plants; contains 36 families including Magnoliaceae and
         Ranunculaceae; sometimes classified as a superorder [syn:
         Magnoliidae, subclass Magnoliidae, ranalian complex]