signalling vs alarm

signalling and alarm both are nouns.

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

As nouns, alarm is a hyponym of signalling; that is, alarm is a word with a more specific, narrower meaning than signalling:

signalling (noun)	alarm (noun)
any nonverbal action or gesture that encodes a message	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

signalling (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