1. on watch： 值班; （通常指军队夜间的）警戒，值夜，站岗
I am the man on watch today.今天我值班。
I go on watch in an hour.
我一个小时后值班。
The man on watch didn't notice the danger.
值班的人没有注意到这危险。
Tom is the man on watch today.
汤姆就是今天那个值班的人。
Apart from two men on watch in the engine-room, everyone was asleep.
除了两个人在机房值班外，其他人都在睡觉。
The men go on watch when they were working.
这些人上班是值夜班。
Several sailors were on watch.
几个水手正在值班。
I'm on first watch.
我值第一班。
《牛津高阶英汉双解词典》
The guards are still on watch at midnight.
看守在深夜仍在站岗。
He was standing on watch .他在站岗。
Who’s on watch now?谁现在在值班。
2. on the watch（for）：看守着；监视着，提防，留意、警惕、对……密切注视着；对……留神着
Be on the watch for thieves.
要提防小偷。
The guards are on the watch.
警卫们小心警戒。
Environmentalists will be on the watch for damage to wildlife.
环境保护主义者将会密切关注对野生动物造成的伤害。
The customs inspector was on the watch for diamond smugglers.
海关检查员正监视着钻石走私的活动。
《汉英大词典》
smuggler [ˈsmʌɡlə(r)]n. 走私者;复数： smugglers
He took up with smugglers.
他和走私犯混到一块儿去了。
《柯林斯高阶英汉双解学习词典》
Smugglers will face severe penalties.
走私者将面临严厉处罚。
The man on the watch cried out: Dangers ahead!
守望的人突然大喊前面有危险！
The conductor was always on the watch for such doings.
这个指挥总是提防这样的动作。
Be on the watch for thieves in this crowd.
在这些人群中要提防有小偷。
The police were on the watch for any trouble.
警察局提防出现任何乱子。
Grace is still on the watch for the wounded boy.
格蕾丝仍在守候着那个受伤的男孩。
The staff are always on the watch for shoplifters.
商店的员工们总是警惕着行窃的扒手。
shoplifters [ˈʃɒpˌlɪftəz] shoplifter的复数，扒手
Shoplifters will be prosecuted.
在本店行窃者将被起诉。
