pratmobile
A car which has been modified in such a way that the owner and his friends think it's the bee's knees but everybody else thinks it makes (usually) him or (rarely) her look a complete knob head. The typical pratmobile is a small, practical, inoffensive car such as a VW Polo, Ford Fiesta, Vauxhall Corsa, or even a Fiat Panda, that has had a seriously loud and illegal megaphone exhaust fitted and possibly dropped suspension, and is piloted by somebody who fondly imagines that he can drive like Lewis Hamilton. It may also be a larger family car that has been inappropriately tarted up.
Rodney (to Del Boy): "You take the van and I … no, I'll take the van and you take the pratmobile."