kiss of peace vs greeting

kiss of peace and greeting both are nouns.

Word	Noun	Adjective	Verb	Adverb
kiss of peace	Yes	No	No	No
greeting	Yes	No	No	No

As nouns, greeting is a hypernym of kiss of peace; that is, greeting is a word with a broader meaning than kiss of peace:

kiss of peace: (Roman Catholic Church) a greeting signifying Christian love for those assisting at the Eucharist
greeting: (usually plural) an acknowledgment or expression of good will (especially on meeting)

Other hypernyms of kiss of peace include salutation.

kiss of peace (noun)	greeting (noun)
(Roman Catholic Church) a greeting signifying Christian love for those assisting at the Eucharist	(usually plural) an acknowledgment or expression of good will (especially on meeting)