·add. ·noun = Tonne.
II. Tonneau ·add. ·noun In France, a light-wheeled vehicle with square or rounded body and rear entrance.
III. Tonneau ·add. ·noun Orig., the after part of the body with entrance at the rear (as in vehicle in def. 1); now, one with sides closing in the seat or seats and entered by a door usually at the side, also, the entire body of an automobile having such an after part.