brain truster vs adviser

brain truster and adviser both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain truster	Yes	No	No	No
adviser	Yes	No	No	No

As nouns, adviser is a hypernym of brain truster; that is, adviser is a word with a broader meaning than brain truster:

brain truster: an expert adviser involved in making important decisions but usually lacking official status
adviser: an expert who gives advice

Other hypernyms of brain truster include advisor, consultant.

brain truster (noun)	adviser (noun)
an expert adviser involved in making important decisions but usually lacking official status	an expert who gives advice