all clear vs signal

all clear and signal both are nouns.

Word	Noun	Adjective	Verb	Adverb
all clear	Yes	No	No	No
signal	Yes	Yes	Yes	No

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

Other hypernyms of all clear include sign, signaling, signalling.

all clear (noun)	signal (noun)
a signal (usually a siren) that danger is over	any nonverbal action or gesture that encodes a message
permission to proceed because obstacles have been removed	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

all clear (adjective)	signal (adjective)
	notably out of the ordinary

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