keep an eye out (for (someone/something))

to watch carefully for someone or something.

Three aircraft kept an eye out for the submarine while waiting for help to arrive.

I always kept my eye out for strangers.

Related vocabulary: keep a close watch on someone/something, keep an ear out for someone/something

• at someone's knee
• at someone's service
• at stake
• attend to
• attend to someone
• attend to something
• at the back of beyond
• at the back of mind
• at the back of your mind
• at the best of times
• at the bottom of the heap
• at the bottom of the ladder
• at the bottom of the pile
• at the chalkface
• at the coalface
• at the crack of dawn
• at the cutting edge
• at the double
• at the drop of a hat
• at the eleventh hour
• at the end of the day
• at the expense of
• at the expense of something
• at the hands of
• at the hands of someone