on and off If something happens on and off during a period of time, it happens sometimes. 时断时续地;间歇地 I've had toothache on and off for a couple of months. 我的牙断断续续疼了几个月。 Mike and I were pretty serious for about a year, but our relationship has been off and on ever since we graduated. 麦克和我是认真地谈了有一年了，但是自从我们毕业后，我们的关系就断断续续时好时坏的。