A Battlewagon is a catch-all term used for any type of Ork assault tank and heavy armoured troop transport. The term Battlewagon seems to refer overall to a category of large Ork armoured vehicles. A Battlewagon can be wheeled, tracked or a combination of the two and is used in many battlefield roles. It always carries a large complement of weapons.
Sometimes these armaments are just Big Shootas, while on other vehicles they are large Killkannons. Battlewagons possess thick armour plating, multiple turrets and death rollers or rams. They also carry mobs of Ork Boyz, either internally or clinging onto its many handholds.
Photographs from Games Day, Warhammer World and models from my collection.