[pil.lion] n [ScGael or Ir; ScGael pillean, dim. of peall covering, couch; Ir pillin, dim. of peall covering, couch] (1503) 1 a: a light saddle for women consisting chiefly of a cushion b: a pad or cushion put on behind a man's saddle chiefly for a woman to ride on
2. chiefly Brit: a motorcycle or bicycle saddle for a passenger
[2]pillion adv (1926) chiefly Brit: on or as if on a pillion "ride ~"