rumble seat

noun2

1. •
   (informal) A jump seat.
2. •
   (old-fashioned) An extra passenger seat or row of seats in a carriage or automobile, typically folding away into a rear storage compartment.

   • Vito does a lot of his own felting, dealing direct with Indians who are apt to show up here at all hours with a rumble seat full of beaver hides […]. — 2025