For the purpose of these rules, the following words and phrases will have the following meanings:
"Bump-fire stock" means a butt stock designed to be attached to a semiautomatic firearm with the effect of increasing the rate of fire achievable with the semiautomatic firearm to that of a fully automatic firearm by using the energy from the recoil of the firearm to generate reciprocating action that facilitates repeated activation of the trigger.
Wash. Admin. Code § 446-100-015