Automatic firearm

firearm which continuously loads and fires supplied ammunition

An automatic firearm is a firearm that automatically extracts and ejects the fired cartridge case, and loads a new case, usually through the energy of the fired round. The term can be used to refer to semi-automatic firearms, which fire one shot per pull of the trigger, or fully automatic firearms, which will continue to load and fire ammunition as long as the trigger (or other activating device) is pressed or until the ammunition is exhausted. "Automatic pistol" or "automatic shotgun" generally refers to a semi-automatic design, while "automatic rifle" more often means a fully automatic or selective fire design.
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Noun
1. a firearm that reloads itself and keeps firing until the trigger is released
(hypernym) autoloader, self-loader
(hyponym) automatic pistol, automatic