Webster's Revised Unabridged Dictionary · 1913

Whap

Whap , intransitive verb

[Compare Old English quappen to palpitate, English quob, quaver, wabble, awhape, wap.]

To throw one's self quickly, or by an abrupt motion; to turn suddenly; as, she whapped down on the floor; the fish whapped over. — Bartlett

This word is used adverbially in the north of England, as in the United States, when anything vanishes, or is gone suddenly; as, whap went the cigar out of my mouth.

Also: Whop

Whap , transitive verb

To beat or strike.

Also: Whop

Whap , noun

A blow, or quick, smart stroke.

Also: Whop