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3. be on full alert

be on full alert

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be on full alert

To be very attentive and ready to take action. This term is often applied to soldiers. We're safe here—the soldiers patrolling the border are on full alert. As soon as I heard my window break in the middle of the night, I was on full alert to fight off an intruder.

See also: alert, full, on

be on full/red alert

if soldiers are on full alert, they know that a situation is dangerous and are prepared to act immediately if necessary The British flagship in the area went to battle stations and remained on full alert for twenty minutes.

See also: alert, full, on