i guess there’s no definition that is set in stone but personally a sleeper to me is a car that doesn’t look like it’s built or modified for speed but it can lay down the power
e.g an RB26 transplanted camry, a Turbo’d K24 civic or a 1JZ TA22 Celica
You just don’t expect them to be making the power they do just by looking at them
They are pretty much the cars that go with the phrase “Don’t judge a book by it’s cover”
This is purely my opinion and explaination
Sleepers tend to need a lot of work too :P I love it when people look at my 1978 Cutlass and think I’m poor or I’m full of s***. Sleepers need to thrill the driver and make people wonder how your going fast. If modifications are noticeable then your car isn’t a sleeper.