treadmill
n. countablen. a piece of exercise equipment with a moving belt that you walk or run on while staying in one place.
n. an exercise machine consisting of a continuous moving belt on which a person walks or runs. Often used metaphorically to describe a repetitive, exhausting task or lifestyle that seems to have no end.
I run on the treadmill for thirty minutes every morning.
After a long day at the office, she finds that a brisk walk on the treadmill helps her clear her head.
Many young professionals find themselves trapped on a corporate treadmill, working increasingly long hours to maintain a lifestyle they are too exhausted to actually enjoy.
From tread + mill. Its figurative senses refer to the idea that running on a treadmill requires continued effort and motion to remain in the same place.
Commonly used with the preposition 'on'.