根據具體情境判斷,如下：
head off
1.
攔截,上前攔住(使其轉向或退回):
The running thief was headed off by the police.
那名奪路飛逃的小偷讓警察給攔截住了.
2.
擺脫(跟蹤者)；使改變話題:
From my house out,you have to head off several tails.
從我這兒出去,你得拋掉幾個尾巴.
It's difficult to head her off when she talked about her dissolute life.
要是她談起她的風流韻事來,你就別想岔開她的話題.
3.
防止；回避:
It's better for you to head off his coming.
你最好別讓他來.
Talking with her,you'd try to head off your happy marrige.
和她交談時你最好設法不去談你的幸福的婚姻生活.
4.
趕在別人之前到達(某一重要地方):
It's important to head off the enemy from the airport.
搶在敵人之前占據飛機場是至關重要的.