Pillion /(?)/

Pil·lion

Pillion

n.
  1. A panel or cushion saddle; the under pad or cushion of saddle; esp., a pad or cushion put on behind a man's saddle, on which a woman may ride.
    His [a soldier's] shank pillion without stirrups.
  2. A saddle or seat behind the driver's saddle on a motorcycle, used by passengers.