alarm bell vs alarm

alarm bell and alarm both are nouns.

Word	Noun	Adjective	Verb	Adverb
alarm bell	Yes	No	No	No
alarm	Yes	No	Yes	No

As nouns, alarm is a hypernym of alarm bell; that is, alarm is a word with a broader meaning than alarm bell:

Other hypernyms of alarm bell include alarum, alert, warning signal.

alarm bell (noun)	alarm (noun)
the sound of an alarm (usually a bell)	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

alarm bell (verb)	alarm (verb)
	warn or arouse to a sense of danger or call to a state of preparedness
	fill with apprehension or alarm; cause to be unpleasantly surprised