side-saddle

/S AY1 D S AE0 D AH0 L/
noun
  1. 1

    A saddle, usually for a woman, in which the rider sits with both legs on the same side of the horse.

adverb
  1. 1

    On, or as if on, such a saddle.

    โ€œHe had his daughter riding sidesaddle on the bicycle frame while he pedaled.โ€

Source: https://en.wiktionary.org/wiki/side-saddle, https://en.wiktionary.org/wiki/sidesaddle