sidesaddle
noun [ C ], adverb uk/ˈsaɪdˌsæd.əl/ us/ˈsaɪdˌsæd.əl/
（旧时的）女式马鞍，偏座鞍;偏坐在马鞍上，在偏座鞍上
(on) a saddle used especially in the past by women, on which the rider sits with both legs on the same side of the horse
The Queen rode sidesaddle when she inspected the soldiers. 女王偏坐在马鞍上骑马检阅士兵。