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WordNet
automatic firearm

n. a firearm that reloads itself and keeps firing until the trigger is released

Wikipedia
Automatic firearm

An automatic firearm continuously fires rounds as long as the trigger is pressed or held and there is ammunition in the magazine/ chamber. In contrast, a semi-automatic firearm fires one round with each individual trigger-pull.

Although both "semi automatic" and "fully automatic" firearms are "automatic" in the technical sense that the firearm automatically cycles between rounds with each trigger pull, the terms "automatic weapon" and "automatic firearm" are conventionally reserved by firearm enthusiasts to describe fully automatic firearms. Use of this convention can avoid confusion. Firearms are further defined by the type of firearm action used.

Usage examples of "automatic firearm".

If they possessed a full automatic firearm, they could have cut down the Soviets a hundred meters back.

It's easy as pie to get a weapon past inspection, unless it's some heavy duty automatic firearm or a bomb.