A howitzer that propels itself. Laymen think these are tanks, but their armour is thinner and they haven't got a rotating turret. They are not to be confused with tank destroyers such as the WWII Jagdpanther oder Marder -- tank destroyers are just that, tank destroyers, while self-propelling howitzers are artillery pieces.
Current examples are the U.S. M-109 German PzH 2000.