| 1. | (in military or civilian defense) the most urgent form of alert, signaling that an enemy attack is believed to be imminent. |
| 2. | the signal or alarm sounded for this alert. Compare blue alert, white alert, yellow alert. |
| 3. | a signal or warning that a critical situation is developing or has occurred. |
| 4. | the period during which a state of crisis or danger is declared to exist. |
