1. (noun)treadmill an exercise device consisting of an endless belt on which a person can walk or jog without changing place Synonyms: tread-wheel, saltmine, treadwheel
2. (noun)treadmill, treadwheel, tread-wheel a mill that is powered by men or animals walking on a circular belt or climbing steps Synonyms: tread-wheel, saltmine, treadmill, treadwheel