saddle sore

Short definition from Wiktionary

Noun

1. 1
   A gall, a sore developed by a horse from an ill-fitting or ill-adjusted saddle.
2. 2
   A sore developed by a horseback rider or a cyclist caused by a saddle.

Adjective

1. 1
   Pertaining to a horse with saddle sores, or to a rider who has been riding too long.