grimace vs pull a face

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

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

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

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

Other synonyms of grimace include make a face.

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

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