Grueling means extremely tiring and demanding, pushing you to the limits of your strength or endurance. A grueling hike involves steep climbs, rough terrain, and hours of walking that leave your legs shaking and your lungs burning. A grueling practice session means your coach pushes you harder than usual, making you repeat drills until your muscles ache.

Something grueling tests whether you can keep going when every part of you wants to quit. Marathon runners face a grueling final few miles. Students preparing for important exams might endure a grueling study schedule. Athletes recovering from injuries often face grueling physical therapy.

What makes something grueling is the combination of difficulty, duration, and intensity. Lifting something heavy once is hard, but carrying it uphill for an hour is grueling.