| Noun | 1. | Naiadales - an order of aquatic monocotyledonous herbaceous plants plant order - the order of plants class Liliopsida, class Monocotyledonae, class Monocotyledones, Liliopsida, Monocotyledonae, Monocotyledones - 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 family Naiadaceae, family Najadaceae, naiad family, Naiadaceae, Najadaceae - monotypic family of aquatic plants having narrow leaves and small flowers Alismataceae, family Alismataceae, water-plantain family - perennial or annual aquatic or marsh plants family Hydrocharidaceae, family Hydrocharitaceae, frogbit family, frog's-bit family, Hydrocharidaceae, Hydrocharitaceae - simple nearly stemless freshwater aquatic plants; widely distributed family Potamogetonaceae, pondweed family, Potamogetonaceae - plants that grow in ponds and slow streams; sometimes includes family Zosteraceae arrow-grass family, family Juncaginaceae, family Scheuchzeriaceae, Juncaginaceae, Scheuchzeriaceae - a family of monocotyledonous bog herbs of order Naiadales family Zannichelliaceae, Zannichelliaceae - alternative classification for some genera included in Potamogetonaceae; one species eelgrass family, family Zosteraceae, Zosteraceae - used in some classifications: essentially equivalent to Potamogetonaceae |