Wit in poetry is sharp, clever expression that delights through surprise, irony, or an unexpected turn of thought. It often combines intelligence with brevity, letting a poet say something pointed or funny in a few well-chosen words.
Older criticism also used wit to mean mental brilliance or imagination, but in poetry it usually refers to verbal skill and inventive language rather than simple humor.
Example
Her smile was a winter sun-
small, pale, and somehow warming the room.