- (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, New York: The Century Co., 1911