foreshadow vs signal

foreshadow is not a noun while signal is a noun.

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

As verbs, signal is a hypernym of foreshadow; that is, signal is a word with a broader meaning than foreshadow:

Other hypernyms of foreshadow include bespeak, betoken, indicate, point.

foreshadow (noun)	signal (noun)
	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

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

foreshadow (verb)	signal (verb)
indicate, as with a sign or an omen	communicate silently and non-verbally by signals or signs
	be a signal for or a symptom of