mousse vs fish mousse

mousse and fish mousse both are nouns.

Word	Noun	Adjective	Verb	Adverb
mousse	Yes	No	Yes	No
fish mousse	Yes	No	No	No

As nouns, fish mousse is a hyponym of mousse; that is, fish mousse is a word with a more specific, narrower meaning than mousse:

Other hyponyms of mousse include chicken mousse.

mousse (noun)	fish mousse (noun)
toiletry consisting of an aerosol foam used in hair styling	mousse made with fish
a light creamy dish made from fish or meat and set with gelatin
a rich, frothy, creamy dessert made with whipped egg whites and heavy cream

mousse (verb)	fish mousse (verb)
apply a styling gel to