backroom boy vs consultant

backroom boy and consultant both are nouns.

Word	Noun	Adjective	Verb	Adverb
backroom boy	Yes	No	No	No
consultant	Yes	No	No	No

As nouns, consultant is a hypernym of backroom boy; that is, consultant is a word with a broader meaning than backroom boy:

backroom boy: an expert adviser involved in making important decisions but usually lacking official status
consultant: an expert who gives advice

Other hypernyms of backroom boy include adviser, advisor.

backroom boy (noun)	consultant (noun)
an expert adviser involved in making important decisions but usually lacking official status	an expert who gives advice