impressive vs signal

impressive is not a noun while signal is a noun.

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

impressive (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

impressive (adjective)	signal (adjective)
making a strong or vivid impression	notably out of the ordinary
producing a strong effect

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