Can either be a beat up rusty old pick up truck of 2X4 or 4x4 suspension; or if you are in the military of your country it is the locker/footlocker you store your "shit", i.e. personal kit in...
eg. 1 There is a shitbox pickup truck contest on at the exhibition grounds in three weeks!!!
eg. 2 Shake out your shitboxes, and line up the contents on your bunks, plugs! Inspection in twenty six mike! the Sergeant shouted, booming....
1.A total and complete piece of shit.
2.Basically, a pile of wreckage that the Navy keeps wanting to fly...even though it has more Maintenance hours than Flight hours.
3 See: C-130T