pull a face vs grimace

pull a face is not a noun while grimace is a noun.

Word	Noun	Adjective	Verb	Adverb
pull a face	No	No	Yes	No
grimace	Yes	No	Yes	No

As verbs, pull a face and grimace are synonyms defined as:

pull a face and grimace: contort the face to indicate a certain mental or emotional state

Other synonyms of pull a face include make a face.

pull a face (noun)	grimace (noun)
	a contorted facial expression

pull a face (verb)	grimace (verb)
contort the face to indicate a certain mental or emotional state	contort the face to indicate a certain mental or emotional state