/ əˈlɜːt; NAmE əˈlɜːrt/ adjective , verb , noun
■ adjective
1.
able to think quickly; quick to notice things :
Suddenly he found himself awake and fully alert.
Two alert scientists spotted the mistake.
2.
alert to sth aware of sth, especially a problem or danger :
We must be alert to the possibility of danger.
► alert·ly adjective
► alert·ness noun [ U ]
■ verb [ often passive ]
1.
to warn sb about a dangerous or urgent situation :
[ vn ]
Neighbours quickly alerted the emergency services.
Alerted by a noise downstairs, he sat up and turned on the light.
[also vn ( that ), vn to inf ]
2.
[ vn ] ~ sb to sth to make sb aware of sth :
They had been alerted to the possibility of further price rises.
■ noun
1.
[ sing. , U ] a situation in which people are watching for danger and ready to deal with it :
Police are warning the public to be on the alert for suspicious packages.
More than 5 000 troops have been placed on (full) alert .
2.
[ C ] a warning of danger or of a problem :
a bomb / fire alert
—see also red alert
••
WORD ORIGIN
late 16th cent. (originally in military use): from French alerte , from Italian all' erta to the watchtower.