mollusc

noun2

1. •
   A soft-bodied invertebrate of the phylum Mollusca, typically with a hard shell of one or more pieces.

   • For example, the antitumour depsipeptide kahalalide F was isolated from the opisthobranch mollusc Elysia rufescens, and is used by both the mollusc and its dietary alga Bryopsis spp. — 2016
2. •
   (figurative) A weak-willed person.