‖ n. pl. [ NL., from Gr. &unr_; hair + &unr_; jaw. ] (Zool) a phylum consisting of the arrowworms, a group of small active transparent free-swimming marine worms, of which the genus Sagitta is the type. They have groups of curved spines on each side of the head. Syn. -- phylum Chaetognatha. [ 1913 Webster + WordNet 1.5 ]