D defs.my
Entry 3 senses Webster, 1913

Capper

/kăp'-ẽr/ · Cap·per · IPA /ˈkæ.pəɹ/
01 n. One whose business is to make or sell caps.
  1. 1.
    One whose business is to make or sell caps.
  2. 2.
    A by-bidder; a decoy for gamblers.[Slang, U. S.]
  3. 3.
    An instrument for applying a percussion cap to a gun or cartridge.