starting signal vs signal

starting signal and signal both are nouns.

Word	Noun	Adjective	Verb	Adverb
starting signal	Yes	No	No	No
signal	Yes	Yes	Yes	No

As nouns, signal is a hypernym of starting signal; that is, signal is a word with a broader meaning than starting signal:

Other hypernyms of starting signal include sign, signaling, signalling.

starting signal (noun)	signal (noun)
a signal to begin (as in a race)	any nonverbal action or gesture that encodes a message
	any incitement to action
	an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

starting signal (adjective)	signal (adjective)
	notably out of the ordinary

starting signal (verb)	signal (verb)
	communicate silently and non-verbally by signals or signs
	be a signal for or a symptom of