fogsignal vs alarm

fogsignal and alarm both are nouns.

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

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

Other hypernyms of fogsignal include alarum, alert, warning signal.

fogsignal (noun)	alarm (noun)
a loud low warning signal that can be heard by fogbound ships	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

fogsignal (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