sulky

Concise Oxford English Dictionary © 2008 Oxford University Press:
sulky/ˈsʌlki/

▶adjective (sulkier, sulkiest) morose, bad-tempered, and resentful. ▶noun (pl. sulkies) a light two-wheeled horse-drawn vehicle for one person, used chiefly in trotting races.

– derivatives
sulkily adverb,
sulkiness noun.

– origin C18: perh. from obs. sulke ‘hard to dispose of’, of unknown origin.