A car, usually a small one such as a Ford Ka or Fiat 500, (Tin can) crammed with attractive, excitable young women. tarts
Most commonly seen on the highways at the start / end of college semesters. If you're driving something cool / unusual / vintage, they tend to get dizzy and play 'car leapfrog' or try and take photos of you.
Passenger: Hey, old Renault Clio coming past, fulla girls.
Driver: Tinned tart!