Thwack

Part of speech: noun (n.)

A heavy blow with something flat or heavy; a thump. With many a stiff thwack, many a bang, Hard crab tree and old iron rang. Hudibras.

Part of speech: verb (v.)

1. To strike with something flat or heavy; to bang, or thrash: to thump. "A distant thwacking sound." W. Irving.

2. To fill to overflow. [Obs.] Stanyhurst.