smiler vs countenance

smiler and countenance both are nouns.

Word	Noun	Adjective	Verb	Adverb
smiler	Yes	No	No	No
countenance	Yes	No	Yes	No

As nouns, smiler and countenance are synonyms defined as:

smiler and countenance: the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)

Other synonyms of smiler include kisser, mug, phiz, physiognomy, visage.

smiler (noun)	countenance (noun)
the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)	the appearance conveyed by a person's face
a person who smiles	the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)
	formal and explicit approval

smiler (verb)	countenance (verb)
	consent to, give permission; permit