derny
noun [ C ] sports UK specialized uk/ˈdɜː.ni / us/ˈdɜ˞ː.ni / (also derny bike, /ˈdɜː.ni ˌbaɪk/ /ˈdɜ˞ː.ni ˌbaɪk/)
（在如竞轮等一些自行车比赛中用来设定速度的）电动自行车，电单车
a bicycle with a motor, used to set the pace (= speed) in some bicycle racing events such as the keirin