treadmill

n. 1 device for producing motion by the weight of persons or animals stepping on steps attached to a revolving upright wheel. 2 similar device used for exercise. 3 monotonous routine work.

n. A mill worked by persons treading upon steps on the periphery of a wide wheel having a horizontal axis. It is used principally as a means of prison discipline. Also, a mill worked by horses, dogs, etc., treading an endless belt.