portrait painter vs painter

portrait painter and painter both are nouns.

Word	Noun	Adjective	Verb	Adverb
portrait painter	Yes	No	No	No
painter	Yes	No	No	No

As nouns, painter is a hypernym of portrait painter; that is, painter is a word with a broader meaning than portrait painter:

portrait painter (noun)	painter (noun)
a painter or drawer of portraits	large American feline resembling a lion
	a line that is attached to the bow of a boat and used for tying up (as when docking or towing)
	an artist who paints
	a worker who is employed to cover objects with paint