Definify.com
Webster 1913 Edition
Capper
Cap′per
,Noun.
1.
One whose business is to make or sell caps.
2.
A by-bidder; a decoy for gamblers.
[Slang, U. S.]
3.
An instrument for applying a percussion cap to a gun or cartridge.
Webster 1828 Edition
Capper
CAPPER
,Noun.