WordNet (r) 3.0 (2006):

class Liliopsida
    n 1: comprising seed plants that produce an embryo with a single
         cotyledon and parallel-veined leaves: includes grasses and
         lilies and palms and orchids; divided into four subclasses
         or superorders: Alismatidae; Arecidae; Commelinidae; and
         Liliidae [syn: Monocotyledones, class Monocotyledones,
         Monocotyledonae, class Monocotyledonae, Liliopsida,
         class Liliopsida]