1. (a) A light saddle women consisting chiefly of a cushion.
(b) A pad or cushion put behind a man’s saddle chiefly for a woman to ride on.
2. (British) A motorcycle or bicycle saddle for a passenger.
On or as if on a pillion.
Deriving from the Gaelic peall for “covering” or “couch,” “pillion” is a nice word to know when mounted transportation comes up. Now don’t get riled up – of course a woman can ride on a normal saddle and by herself, but a lady of high birth is a lot more likely to ride in comfort.
And of course if you’re writing that Mad Max-style scifi adventure romp, you can throw in some pillion seating. Someone’s gotta hold the flamethrower, after all.
They mounted the fine steed whose bridle was marked with a coronet, the girl riding pillion, and they turned westward, since the girl said this was best. For, as she now told Jurgen, she was Guenevere, the daughter of Gogyrvan, King of Glathion and the Red Islands. So Jurgen told her he was the Duke of Logreus, because he felt it was not appropriate for a pawnbroker to be rescuing princesses[…]
– James Branch Cabell, Jurgen, A Comedy of Justice (1922)