- (in military or civilian defense) the first alert given when enemy aircraft are discovered approaching a military installation, city, coastline, etc.Compare blue alert, red alert, white alert.
- the signal or alarm sounded for this alert.
- any primary stage of alert, as when toxic chemicals have escaped in a particular area and a potential hazard exists.
Origin of yellow alert
First recorded in 1965–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018