The Paddock Bomb is a vehicle that can be found sitting beside the shed, rusting away on every farm in Australia. Usually it is a car that is well past its used-by date and no longer able to be driven on the roads (legally). It is the car you allow your children to tear up the paddocks in, doing doughnuts and harassing the local livestock. Good clean fun to have when they bring friends home, out in the fresh air and having fun.
Even though most of them have modifications such as the exhaust being a can of some sort or the door being held on by baling twine or non-existent, it is thought by most parents that it is a safer option than having the kids hanging around 'in town'.
The local lads will take the paddock bomb out spotlighting for rabbits and foxes. Taking it cross-country at high speed in pursuit of a feral animal, not worrying about the panel work or the suspension. Or their lives for that matter at times.
Generally once the paddock bomb is no longer running and can not be repaired they are left to rot at the back of the shed and become home to many small animals and birds.
The Australian Macquarie Dictionary has this definition.
Paddock-basher: noun Colloquial: a heavy duty motor vehicle suited to driving on difficult terrain.