Pil"lion (?), n. [Ir. pillin, pilliun (akin to Gael. pillean, pillin), fr. Ir. & Gael. pill, peall, a skin or hide, prob. fr. L. pellis. See Pell, n., Fell skin.]
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.
Spenser.
© Webster 1913.