It means unhappily or with sadness.
I stared into his eyes gloomily. He grimaced then struck me in the face.
The word gloomily is an adverb. It means to do something in a gloomy manner.
be pessimistic
The adverb refers to acting in a depressed or labored manner, or to a setting that appears dreary, dull, or dark. Examples: She went outside and sat gloomily on the stone bench. The economists gloomily predicted another month of recession. At night, the town square was gloomily lit by a half dozen gas lamps.
think negatively
Gloomily.
Antonyms: doubtfully, gloomily, hopelessly
gloomily
Gloomily and sorrowfully.
despondently, forlornly, gloomily, glumly, sadly, sorrowfully, unpleasantly
Two adverbs that can be used to describe sadness are "gloomily" and "mournfully."
Sullenly means acting with ill grace. Acting bad-tempered, sullenly, gloomily.