California Code, Penal Code - PEN § 16930

(1) A device designed or redesigned to be attached to, built into, or used in conjunction with, a semiautomatic firearm, which allows the firearm to discharge two or more shots in a burst by activating the device.

(2) A manual or power-driven trigger activating device constructed and designed so that when attached to, built into, or used in conjunction with, a semiautomatic firearm it increases the rate of fire of that firearm.

(1) A device that uses a spring, piston, or similar mechanism to push back against the recoil of a firearm, thereby moving the firearm in a back-and-forth motion and facilitating the rapid reset and activation of the trigger by a stationary finger. These devices are commonly known as bump stocks, bump fire stocks, or bump fire stock attachments.

(2) A device placed within the trigger guard of a firearm that uses a spring to push back against the recoil of the firearm causing the finger in the trigger guard to move back and forth and rapidly activate the trigger. These devices are commonly known as burst triggers.

(3) A mechanical device that activates the trigger of the firearm in rapid succession by turning a crank. These devices are commonly known as trigger cranks, gat cranks, gat triggers, or trigger actuators.

(4) Any aftermarket trigger or trigger system that, if installed, allows more than one round to be fired with a single depression of the trigger.