WordNet (r) 3.0 (2006):

Commelinidae
    n 1: one of four subclasses or superorders of Monocotyledones;
         comprises about 19,000 species in 25 families of mostly
         terrestrial herbs especially of moist places including:
         Cyperaceae; Gramineae; Bromeliaceae; and Zingiberaceae
         [syn: Commelinidae, subclass Commelinidae]