wagon seat

a plain, unupholstered settee, usually with a slat back, for use either indoors or in a wagon.

Also called rumble seat.

Origin of wagon seat

An Americanism dating back to 1850–55

He clambered down, leaving the speechless Ole sprawling on the wagon-seat.

A Breath of Prairie and other stories |Will Lillibridge
That thing you see sitting up on that wagon-seat there—call that a man?

Twelve Men |Theodore Dreiser
Uncle Enoch, wakened from the half doze which he had been taking on the wagon-seat, now began to saw on the lines.

Horses Nine |Sewell Ford
There was no use looking for it, or advertising for it; he knew that it was on that wagon-seat.

Golden Days for Boys and Girls |Various

She looked colossal up on the wagon-seat, but when she got down on the ground she was not so immense.

The Prairie Wife |Arthur Stringer