sea slug vs nudibranch

sea slug and nudibranch both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea slug	Yes	No	No	No
nudibranch	Yes	No	No	No

As nouns, sea slug and nudibranch are synonyms defined as:

sea slug and nudibranch: any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body

sea slug (noun)	nudibranch (noun)
any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body	any of various marine gastropods of the suborder Nudibranchia having a shell-less and often beautifully colored body