Polychaeta n 1: marine annelid worms [syn: {Polychaeta}, {class Polychaeta}]
Polychaeta \Pol`y*ch[ae]"ta\, n. pl. [NL., from Gr. poly`s many + ? hair.] (Zool.) One of the two principal groups of Ch[ae]topoda. It includes those that have prominent parapodia and fascicles of set[ae]. See Illust. under {Parapodia}. [1913 Webster]
Annelida \An*nel"i*da\, n. pl. [NL. See {Annelid}.] (Zool.) A division of the Articulata, having the body formed of numerous rings or annular segments, and without jointed legs. The principal subdivisions are the {Ch[ae]topoda}, including the {Oligoch[ae]ta} or earthworms and {Polych[ae]ta} or marine worms; and the {Hirudinea} or leeches. See {Ch[ae]topoda}. [1913 Webster]