chor·date / ˈkôrdət; -ˌdāt/ • n. any animal of the phylum Chordata, including all vertebrates as well as the invertebrate sea squirts and lancelets, distinguished by the possession of a notochord at some stage during their development.• adj. of or related to the chordates.

chordate Any member of the Chordata, a large phylum of vertebrates and some marine invertebrates, which, at some stage, have rod-like, cartilaginous supporting structures (notochords). Invertebrate chordates are divided into three subphyla: tunicates (seasquirts); Cephalochordata (amphioxus); and Hemichordata (acorn worms).