treadmill vs treadwheel

treadmill and treadwheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
treadmill	Yes	No	No	No
treadwheel	Yes	No	No	No

As nouns, treadmill and treadwheel are synonyms defined as:

treadmill and treadwheel: a mill that is powered by men or animals walking on a circular belt or climbing steps

Other synonyms of treadmill include tread-wheel.

treadmill (noun)	treadwheel (noun)
a job involving drudgery and confinement	a mill that is powered by men or animals walking on a circular belt or climbing steps
a mill that is powered by men or animals walking on a circular belt or climbing steps
an exercise device consisting of an endless belt on which a person can walk or jog without changing place