grimace vs glower

grimace and glower both are nouns.

Word	Noun	Adjective	Verb	Adverb
grimace	Yes	No	Yes	No
glower	Yes	No	Yes	No

As verbs, glower is a hyponym of grimace; that is, glower is a word with a more specific, narrower meaning than grimace:

grimace: contort the face to indicate a certain mental or emotional state
glower: look angry or sullen, wrinkle one's forehead, as if to signal disapproval

Other hyponyms of grimace include squinch, squint, wince, smile, frown, lour, lower, screw up, mop, mow, pout.

grimace (noun)	glower (noun)
a contorted facial expression	an angry stare

grimace (verb)	glower (verb)
contort the face to indicate a certain mental or emotional state	look angry or sullen, wrinkle one's forehead, as if to signal disapproval
	look at with a fixed gaze