- belonging or pertaining to the chordates of the phylum Hemichordata, comprising small, widely distributed, marine animals, as the acorn worms.
- a hemichordate animal, having a vertebratelike hollow nerve cord and an echinodermlike larval stage.
- any small wormlike marine animal of the subphylum Hemichordata (or Hemichorda), having numerous gill slits in the pharynx: phylum Chordata (chordates)
- of, relating to, or belonging to the subphylum Hemichordata
- Any of various mostly small, wormlike marine invertebrates once thought to be chordates but now considered more closely related to echinoderms. They may constitute their own phylum, the Hemichordata. The bodies of hemichordates are divided into a feeding organ called a proboscis, a ringlike section called a collar, and a trunk. Hemichordates have a gut, circulatory system, and nervous system and are filter feeders. Acorn worms and graptolites are hemichordates.