(US, intransitive) To throw oneself quickly, or by an abrupt motion; to turn suddenly.
1844, Thomas Chandler Haliburton, Judge Haliburton’s Yankee Stories, Part Two, Chapter 22, Philadelphia: Lindsay & Blakiston, pp. 179-180,
He wears his hat a little a one side, rakish-like, whaps his cane down ag’in the pavement hard, as if he intended to keep things in their place, swaggers a few, as if he though he had a right to look big […]
She whapped down on the floor.
The fish whapped over.
interjection
The sound of sudden blow or hit.
noun
(Scotland, obsolete) The curlew, Numenius arquata; a whaup.