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on the alert

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on the alert (for someone or something)

watchful and attentive for someone or something. Be on the alert for pickpockets. You should be on the alert when you cross the street in heavy traffic.

See also: alert, on

on the alert

Watchful, fully prepared, as in The inspectors are always on the alert for a manufacturing error. [Late 1700s]

See also: alert, on

on the alert

Watchful and prepared for danger, emergency, or opportunity: bird watchers on the alert for a rare species.

See also: alert, on