Both "Assault-Style Weapon" is a term made up by the media to make people think they know what the hell they're talking about. But if you want to use the Army defined definition, here it is: By U.S. Army definition, a selective-fire rifle chambered for a cartridge of intermediate power. If applied to any semi-automatic firearm regardless of its cosmetic similarity to a true assault rifle, the term is incorrect. Assault Weapon. Any weapon used in an assault.