signal vs all clear

signal and all clear both are nouns.

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

As nouns, all clear is a hyponym of signal; that is, all clear is a word with a more specific, narrower meaning than signal:

signal (noun)	all clear (noun)
any nonverbal action or gesture that encodes a message	a signal (usually a siren) that danger is over
any incitement to action	permission to proceed because obstacles have been removed
an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

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

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