thwapping

Thwapping is the present participle of thwap, an onomatopoeic verb describing a sharp slapping or smacking sound, or the action that produces it.

The word evokes a flat object striking a surface with moderate force—a newspaper thwapping against a table, a bird's wings thwapping the air.

She kept thwapping her pen against her notebook during the meeting.

It carries slightly more comic energy than similar words like slapping or whacking.