noun
idle pulley; idler pulley
Mechanical term for a pulley that guides or tensions a belt without transmitting power itself.
エンジンのベルト駆動系には遊び車が使われている。
An idle pulley is used in the engine's belt drive system.
Katakana loanword for the same mechanical part; 遊び車 is the native Japanese term.
Compound of 遊び (asobi, 'play' or 'idle') and 車 (kuruma, 'wheel'), referring to a wheel that rotates freely without transmitting power.