'Nudibranch' definitions:

Definition of 'nudibranch'

noun

Any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body [syn: sea slug, nudibranch]

From: GCIDE

Nudibranch \Nu"di*branch\, a. (Zool.) Of or pertaining to the Nudibranchiata. -- n. One of the Nudibranchiata. [1913 Webster]