"treadmills" in the noun sense
an exercise device consisting of an endless belt on which a person can walk or jog without changing place
2. treadmill, treadwheel, tread-wheel
a mill that is powered by men or animals walking on a circular belt or climbing steps
3. treadmill, salt mine
a job involving drudgery and confinement
Source: WordNet® (An amazing lexical database of English)
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