grimace vs lour

grimace is a noun but lour is not a noun.

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

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

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

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

grimace (noun)	lour (noun)
a contorted facial expression

grimace (verb)	lour (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
	make lower or quieter
	set lower