| Noun | 1. | Peridiniidae - marine and freshwater dinoflagellates protoctist family - any of the families of Protoctista Cilioflagellata, Dinoflagellata, order Cilioflagellata, order Dinoflagellata - in some classifications considered a phylum of the kingdom Protista; in others included in the plant phylum Pyrrophyta genus Peridinium, Peridinium - type genus of the family Peridiniidae peridinian - flagellate with a thick test composed of plates |