To be silent and refuse to be friendly or to smile because you are angry about something.
Sulking can make people feel sad or annoyed.
Examples:
She sulked in her room after her friends didn't invite her to play.
He sulked all day because he didn't get the toy he wanted.
The little girl sulked when her ice cream fell on the ground.
The cat sulked because it didn't get any fish.
He sulked for a whole week because he lost his favorite game.
The dog sulked under the table when it didn't get any food.