‖n. pl. [ NL., fr. Gr. ke`ras, ke`ratos, horn + &unr_;, n. pl., gills. ] (Zool.) A group of nudibranchiate Mollusca having on the back papilliform or branched organs serving as gills. [ 1913 Webster ]

a. (Anat.) Pertaining to the bone, or cartilage, below the epibranchial in a branchial arch. -- n. A ceratobranchial bone, or cartilage. [ 1913 Webster ]