Definition of tonneau:
(n) :
The rear body or compartment of some types of motor vehicle, especially one containing seats for passengers.
(n) :
An old-style open passenger vehicle with a tonneau (rear compartment with seats).
(n) :
Clipping of tonneau cover. [(automotive) A protective covering which may be secured over the exposed portion of a motor vehicle, such as the seating area of an open sports car or the back of a pickup truck.]