short for fixed-gear bike or fixed-wheel bike: a bicycle with only one gear (= a device that controls how much power goes to the wheels of a vehicle) that cannot move unless the pedals are being turned, often used for getting around a city

I recently rode my friend's fixie in San Francisco and now I want one for myself. 我最近在旧金山骑了我朋友的单速自行车，现在我也想给自己买一辆。

The beauty of the fixie is its elegant simplicity.