indicator vs signalling

indicator and signalling both are nouns.

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

As nouns, signalling is a hypernym of indicator; that is, signalling is a word with a broader meaning than indicator:

Other hypernyms of indicator include sign, signal, signaling.

indicator (noun)	signalling (noun)
a device for showing the operating condition of some system	any nonverbal action or gesture that encodes a message
a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time
a signal for attracting attention
(chemistry) a substance that changes color to indicate the presence of some ion or substance; can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction