wiretap vs investigation

wiretap and investigation both are nouns.

Word	Noun	Adjective	Verb	Adverb
wiretap	Yes	No	Yes	No
investigation	Yes	No	No	No

As nouns, investigation is a hypernym of wiretap; that is, investigation is a word with a broader meaning than wiretap:

wiretap: the act of tapping a telephone or telegraph line to get information
investigation: the work of inquiring into something thoroughly and systematically

Other hypernyms of wiretap include investigating.

wiretap (noun)	investigation (noun)
the act of tapping a telephone or telegraph line to get information	the work of inquiring into something thoroughly and systematically
	an inquiry into unfamiliar or questionable activities

wiretap (verb)	investigation (verb)
tap a telephone or telegraph wire to get information