Final answer:
The 11-letter word that means sulky or peevish is 'petulant'. It describes someone irritable or easily annoyed by trivial matters.
Step-by-step explanation:
The 11-letter word that means sulky or peevish is petulant. This word is often used to describe someone who is irritable or quickly annoyed, especially over small matters. It's useful in literature or daily communication to characterize an individual who shows sudden, impatient irritation, like a sulky child who is unhappy and displays unreasonable upset over not getting their way.