Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

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