alert noun

ADJ. red His sudden disappearance triggered a red alert among his friends. | nationwide | bomb, fire, flood, pollution, security A security alert was issued after four men escaped from the prison.

VERB + ALERT issue, put out, raise, sound They rang the church bells to sound the alert and the villagers then fled. | spark, trigger | call off The alert was called off when it was found that the bomb was not live.

ALERT + VERB go out A nationwide alert went out for three escaped prisoners.

PREP. on the ~ | ~ for You should always be on the alert for anyone who looks suspicious.

PHRASES be on full alert The security forces are now on full alert. | keep/put/place sb on full alert Thousands of police were put on full alert at all main roads leading to the city. | a state of alert The army was yesterday placed on a state of alert in case of more riots.