brainiac vs intellect

brainiac and intellect both are nouns.

Word	Noun	Adjective	Verb	Adverb
brainiac	Yes	No	No	No
intellect	Yes	No	No	No

As nouns, intellect is a hypernym of brainiac; that is, intellect is a word with a broader meaning than brainiac:

Other hypernyms of brainiac include intellectual.

brainiac (noun)	intellect (noun)
someone who has exceptional intellectual ability and originality	the capacity for rational thought or inference or discrimination
	knowledge and intellectual ability
	a person who uses the mind creatively