Alarm

1. An electrical, electronic, or mechanical device that serves to warn of danger by means of a sound or signal. The alarm bell warned us of a possible tidal wave.
2. A sudden fear caused by the realization of danger. I was alarmed when I saw the tiger.
3. A warning of existing or approaching danger. She was alarmed about the loss of feeling in her hands.
4. A musical or mechanical noise used to call for attention. We set the alarm clock for six in the morning.
5. Advice to beware, as of a person or thing. We need to alarm them about the dangers of sun burn.