The Collaborative International Dictionary of English v.0.48:

Dinoflagellata \Dinoflagellata\ n.
   and order of plankton, in some classifications it is
   considered a phylum of the kingdom Protista; in others it is
   included in the plant phylum Pyrrophyta. Its members usually
   have two flagella, one of which extends from its center.

   Syn: order Dinoflagellata, Cilioflagellata, order
        Cilioflagellata.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

Dinoflagellata
    n 1: in some classifications considered a phylum of the kingdom
         Protista; in others included in the plant phylum Pyrrophyta
         [syn: Dinoflagellata, order Dinoflagellata,
         Cilioflagellata, order Cilioflagellata]