bump stock

[ buhmp stok ]

noun

1. a replacement gunstock that enables a semiautomatic rifle to discharge bullets at a much higher rate of fire, nearly that of a fully automatic machine gun.

Word History and Origins

Origin of bump stock¹

First recorded in 2005–10; short for bump fire (from its use of the recoil to bump the trigger against the trigger finger) + (gun)stock ( def )