Fishlike animals having a notochord rather than a true spinal column

Wiktionary Word definitions in Wiktionary
a. Of or pertaining to these creatures. n. Any of the primitive fishlike creatures, of the subphylum ''Cephalochordata'', including the lancets, that lack a true spine but have a notochord which, in the case of cephalochordates, reaches into the head, contrary ...

WordNet Word definitions in WordNet
n. fishlike animals having a notochord rather than a true spinal column

Wikipedia Word definitions in Wikipedia
A cephalochordate (from Greek : κεφαλή kephalé, "head" and χορδή khordé, "chord") is an animal in the chordate subphylum , Cephalochordata , and is defined by the presence of a notochord that persists throughout life. It is represented in the modern oceans ...