glowering vs sullen

glowering and sullen both are adjectives.

Word	Noun	Adjective	Verb	Adverb
glowering	No	Yes	No	No
sullen	No	Yes	No	No

As adjectives, glowering and sullen are synonyms defined as:

Other synonyms of glowering include dark, dour, glum, moody, morose, saturnine, sour.

glowering (adjective)	sullen (adjective)
showing a brooding ill humor	darkened by clouds
	showing a brooding ill humor