acorn barnacle vs rock barnacle

acorn barnacle and rock barnacle both are nouns.

Word	Noun	Adjective	Verb	Adverb
acorn barnacle	Yes	No	No	No
rock barnacle	Yes	No	No	No

As nouns, acorn barnacle and rock barnacle are synonyms defined as:

acorn barnacle and rock barnacle: barnacle that attaches to rocks especially in intertidal zones

Other synonyms of acorn barnacle include Balanus balanoides.

acorn barnacle (noun)	rock barnacle (noun)
barnacle that attaches to rocks especially in intertidal zones	barnacle that attaches to rocks especially in intertidal zones