Definitions

1. superlative adjective

most surly or sullen in manner or appearance

“The surliest person in the room refused to participate in the team-building exercise.”

2. noun

a person or thing that is the most surly or sullen

“The surliest customer at the restaurant complained to the manager.”

3. adjective

having a surly or sullen quality

“The surliest of clouds gathered over the city.”