visage vs poker face

visage and poker face both are nouns.

Word	Noun	Adjective	Verb	Adverb
visage	Yes	No	No	No
poker face	Yes	No	No	No

As nouns, poker face is a hyponym of visage; that is, poker face is a word with a more specific, narrower meaning than visage:

visage: the appearance conveyed by a person's face
poker face: a face without any interpretable expression (as that of a good poker player)

Other hyponyms of visage include aspect, expression, face, facial expression, look, devilishness.

visage (noun)	poker face (noun)
the appearance conveyed by a person's face	a face without any interpretable expression (as that of a good poker player)
the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)