wal·lop 
(wŏləp) Informal
(wŏləp) Informal v. wal·loped, wal·lop·ing, wal·lops
v.tr.
1. To beat forcefully; thrash.
2. To strike with a hard blow: walloped the ball into the outfield.
3. To defeat thoroughly.
4. To affect harshly or severely: was walloped with a large fine.
v.intr.
To move in a heavy or clumsy manner.
n.
1. A hard or severe blow.
2.
a. A powerful force: has a punch that delivers a wallop.
b. A powerful effect: "Therein lies the novel's emotional wallop and moral message" (George F. Will).
[Middle English walopen, to gallop, from Old North French *waloper; see wel-1 in the Appendix of Indo-European roots.]
wallop·er n.