1. 电路;(电流的)回路
    An electrical circuit is a complete route which an electric current can flow around.

    e.g. Any attempts to cut through the cabling will break the electrical circuit.
           只要一割断电缆，电路就中断。

2. （尤指工作时的）巡回线路，巡回，巡游
    A circuit is a series of places that are visited regularly by a person or group, especially as a part of their job.

    e.g. He joined the professional circuit...
           他参加了职业巡回赛。
    e.g. It's a common problem, the one I'm asked about most when I'm on the lecture circuit.
           这问题很常见，我在巡回讲演时被问得最多的就是这个问题。

3. 赛车道
    A racing circuit is a track on which cars, motorbikes, or cycles race.

4. (绕着某地的)环行，环游
    A circuit of a place or area is a journey all the way round it.

    e.g. She made a slow circuit of the room.
           她绕着房间缓缓地走了一圈。