a passenger train that is ridden primarily by passengers who travel regularly from one place to another
someone who travels regularly from home in a suburb to work in a city
commuter的用法和样例：
例句
The cops and firefighters knew they might take heat from the hundreds of thousands of subway, bus and commuter line riders, as well as motorists, who would be delayed in the evening rush. 几十万地下铁路、公共汽车以及通勤铁路的乘客，还有自己开车的人，在傍晚下班时交通将受耽搁，警察和救火队员知道那些人将会怪罪他们。
The commuter train is never punctual. 市郊往返列车从来不准点。
Another commuter from the suburban gentry. 来自郊区的又一个通勤者
The five o'clock train is always packed with commuters. 五点钟那趟车总是挤满了通勤者。
