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 pertaining to the opisthobranches.
Also, opisthobranchiate [uh-pis-thuh-brang-kee-it, -eyt] .

1850–55; < Neo-Latin Opisthobranchia the subclass; see opistho-, branchia

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To opisthobranch
World English Dictionary
opisthobranch (əˈpɪsθəˌbræŋk)
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]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Encyclopedia Britannica


any marine gastropod of the approximately 2,000 species of the subclass Opisthobranchia. These gastropods, sometimes called sea slugs, breathe either through gills, which are located behind the heart, or through the body surface. The shell and mantle cavity are reduced or lacking. Larval asymmetry may give way to bilateral symmetry in the adult through a partial untwisting of the embryonic viscera. Reproduction is hermaphroditic-i.e., both male and female reproductive organs occur in one individual.

Learn more about opisthobranch with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Example sentences
Natural products of opisthobranch molluscs: a biological review.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature