on the lookout

Idioms  

1. Also, on the watch. Vigilant, alert, as in Be on the lookout for the twins—they're somewhere on this playground, or He was on the watch for her arrival. Both phrases were originally used with upon. Upon the lookout was originally nautical usage, meaning “on duty being watchful” (as for another ship, rocks, or land); it appeared in the mid-1700s, and on replaced upon about a century later. Upon the watch was first recorded in Daniel Defoe's Robinson Crusoe (1719), and on the watch in Jane Austen's Sense and Sensibility (1797).

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Example Sentences

Be on the lookout for anything that seems too good to be true.

From MarketWatch • Mar. 30, 2026

Despite the misgivings of the scientific community, longevity enthusiasts like Scott and Chitwood are always on the lookout for the next therapy to try.

From Slate • Mar. 30, 2026

A police helicopter was also scrambled to fly at low level over the bare upland hills and farm tracks surrounding the reservoir, on the lookout for vehicles or tents.

From BBC • Mar. 8, 2026

Her daughters — artists Alison and Lezley, and writer Tracye, their mother’s studio director — also stay on the lookout for objects that might catch her eye.

From Los Angeles Times • Feb. 20, 2026

If you’re on the lookout all the time does that mean that you’re scared all the time?

From "The Road" by Cormac McCarthy

Related Words

• active
• bright
• careful
• intelligent
• observant
• perceptive
• sharp
• vigilant
• wary
• watchful
• wired
• wise