Surlily is an adverb used to describe someone's grouchy, sour, or hostile behavior. Some synonyms for this term include sullenly, grumpily, morosely, glumly, peevishly, and ill-naturedly. Other words that share a similar meaning with surlily are crossly, crabby, fractiously, testily, petulantly, and cantankerously. These adverbs are suitable for describing someone who displays a bad mood or a negative attitude towards others. Whether it's due to frustration or dissatisfaction, using these synonyms would help amplify the effect of conveying the intended message in your communication.