signal vs impressive

signal is a noun but impressive is not a noun.

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

signal (noun)	impressive (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

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

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