red flag vs alarm

red flag and alarm both are nouns.

Word	Noun	Adjective	Verb	Adverb
red flag	Yes	No	No	No
alarm	Yes	No	Yes	No

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

Other hypernyms of red flag include alarum, alert, warning signal, flag, signal flag.

red flag (noun)	alarm (noun)
something that irritates or demands immediate action	a device that signals the occurrence of some undesirable event
a flag that serves as a warning signal	a clock that wakes a sleeper at some preset time
the emblem of socialist revolution	an automatic signal (usually a sound) warning of danger
	fear resulting from the awareness of danger

red flag (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