- (zoology) Animals without gills.
- (obsolete) All of those vertebrates that never have gills in their development.
- (dated) A taxonomic order within the phylum Gastropoda — somewhat similar to the clade Nudibranchia.
- (obsolete) A taxonomic order within the phylum Annelida — annelids that lacked specialized respiratory systems, the Oligochaeta, including earthworms.
- Abranchia in The Century Dictionary, The Century Co., New York, 1911