mud run

mud run (plural mud runs)

1. An athletic event in which runners compete to navigate an obstacle course designed to include stretches of mud.
   • 2014, Joe De Sena, Spartan Up!: A Take-No-Prisoners Guide to Overcoming Obstacles and Achieving Peak Performance in Life, page 141:

     I recently received a note from a young man named Austin who had encountered Spartan Race after trying a mud run put on by another promoter.