alarm

a device that signals the occurrence of some undesirable event

a clock that wakes a sleeper at some preset time

an automatic signal (usually a sound) warning of danger

fear resulting from the awareness of danger

warn or arouse to a sense of danger or call to a state of preparedness

The empty house alarmed him

We alerted the new neighbors to the high rate of burglaries

fill with apprehension or alarm; cause to be unpleasantly surprised

I was horrified at the thought of being late for my interview

The news of the executions horrified us