Driving a vehicle (particularly the engine) hard for a few minutes, getting everything fully warmed up and loaded, for the purpose of improving its state of running. Has some theoretical and empirical validity to it (in certain cases, it does actually work), but it can also be an incompetent hackjob substitute for actual mechanical skills and effort (in these cases, it usually makes things worse).
An Italian tuneup is the machinery getting exercise.
That shadetree shop down the road was supposed to fix my engine, but all they did was go for an Italian tuneup, only to stuff it into a tree.
When bad mechanics, usually greasy italian guys, rev the shit out of your engine to try to fix a problem. Usually results in more damage.
Vito's not a real mechanic, all he does is give italian tuneups and say its fixed.