What is Treadmill ?
Treadmill is (noun) 1. a device turned by animals as they walk around a circular path or inside a large wheel Our pet hamster often uses the treadmill in his cage. 2. dull work which has to be done every day His wife complains that her life is a boring treadmill of cooking, cleaning and washing. 3. an exercise machine with a moving belt on which you walk or jog without actually moving forward After ten minutes on the treadmill I’m ready for the jacuzzi.
source: Easier English, Student Dictionary Upper Intermediate Level