on the lookout

on the lookout (for someone or something)

watchful for someone or something. Be on the lookout for signs of a storm. I'm on the lookout for John, who is due here any minute.
See also: lookout, on

on the lookout

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).
See also: lookout, on
References in classic literature ?
My own hand placed it in one of the rouleaux of false half-crowns; and my own hand also directed the spurious coin, when it had been safely packed up, to a certain London dealer who was to be on the lookout for it by the next night's mail.
The French have been on the lookout for that sort of thing.
What boy would dare to play; or whisper, or even glance aside from his book; while Master Cheever is on the lookout behind his spectacles?
Always he was on the lookout for the trail of the gods where it might leave the river and proceed inland.
He must have passed me when he went up last time, for I was on the lookout below bridge here.
Well, I couldn't stay up there forever; so at last I got down, but I kept in the thick woods and on the lookout all the time.
Murthwaite is right, the Indians are likely to be on the lookout at the bank, towards the end of the month too-- and something serious may come of it.
One soon learns to expect this bow and be on the lookout and ready to return it; but to learn to lead off and make the initial bow one's self is a difficult matter for a diffident man.
I did not dare to enter the building, filled as it was with members of the air-scout squadron, who, in common with all Zodanga, were on the lookout for me.
Lawson, on the lookout for models, had discovered a girl who was understudying at one of the theatres, and in order to induce her to sit to him arranged a little luncheon-party one Sunday.
The seventh man was still at large, and was said to be working along the coast on the lookout to steal a canoe and get away to his own island.
She joined them at the moment, on the lookout for any signs of an encouraging result which her treachery might already have produced.
It did not exactly beggar description, but it certainly had that word on the lookout for the mendicancy squad.
I have never seen anything extraordinary, though I am always on the lookout for it everywhere," said Vronsky, smiling.
As it was, they narrowly escaped capture by some privateers from the fifth-form rooms, who were on the lookout for the hot-water convoys, and pursued them up to the very door of their room, making them spill half their load in the passage.