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

• cling hang on by your fingernails
• cling on by your fingertips
• cling on on by fingernails
• cling on on by your fingernails
• clip someone's wings
• clip wings
• clip your wings
• cloak-and-dagger
• clock-watching
• close a sale
• close at hand
• close, but no cigar
• Close, but no cigar.
• close call
• closed-door
• close eyes to
• close eyes to something
• close its eyes to
• close its eyes to something
• close ranks
• close shave
• close the door on
• close the door on something
• close to heart
• close to home