/euh pis"theuh brangk'/ , n.
1. 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.
adj.
2. of or pertaining to the opisthobranches.
Also, opisthobranchiate /euh pis'theuh brang"kee it, -ayt'/ .
[ 1850-55; Opisthobranchia the subclass; see OPISTHO-, BRANCHIA ]