An armored vehicle with the chassis of a tank (but no turret) and a large gun; used as an antitank weapon and to support infantry WordNet 3.0 & Open English WordNet

An assault gun is a type of self-propelled artillery which uses an infantry support gun mounted on a motorized chassis, normally an armored fighting vehicle, which are designed to provide direct fire support for infantry attacks, especially against other infantry or fortified positions. Wikipedia

Self-propelled artillery classification Wikidata