- any gastropod mollusk of the order Opisthobranchia, as the sea slugs, sea butterflies, and sea hares, characterized by a vestigial or absent mantle and shell and two pairs of tentacles.
- of or relating to the opisthobranches.
Also o·pis·tho·bran·chi·ate [uh-pis-thuh-brang-kee-it, -eyt] /əˌpɪs θəˈbræŋ ki ɪt, -ˌeɪt/.
Origin of opisthobranch
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for opisthobranch
C, Diblastula of an Opisthobranch (Polycera) with elongated blastopore oi.
- any marine gastropod of the class Opisthobranchia (or Opisthobranchiata), in which the shell is reduced or absent: includes the pteropods, sea hares, and nudibranchs
via New Latin from Greek opisthen behind + -branch