treadmill

中文： 跑步机

1. A piece of indoor sporting equipment used to allow for the motions of running or walking while staying in one place.
2. A mill worked by persons treading upon steps on the periphery of a wide wheel having a horizontal axis. It was used principally as a means of prison discipline.
3. A mill worked by horses, dogs, etc., treading an endless belt.
4. A process or situation in which continued effort leads to or is required for remaining at a particular state or level without moving ahead. (figuratively)

复数 treadmills