papist vs Roman Catholic

papist and Roman Catholic both are nouns.

Word	Noun	Adjective	Verb	Adverb
papist	Yes	Yes	No	No
Roman Catholic	Yes	Yes	No	No

As adjectives, papist and Roman Catholic are synonyms defined as:

Other synonyms of papist include papistic, papistical, popish, R.C., Roman, Romanist, romish.

As nouns, Roman Catholic is a hypernym of papist; that is, Roman Catholic is a word with a broader meaning than papist:

papist: an offensive term for Roman Catholics; originally, a Roman Catholic who was a strong advocate of the papacy
Roman Catholic: a member of the Roman Catholic Church

papist (noun)	Roman Catholic (noun)
an offensive term for Roman Catholics; originally, a Roman Catholic who was a strong advocate of the papacy	the Christian Church based in the Vatican and presided over by a pope and an episcopal hierarchy
	a member of the Roman Catholic Church

papist (adjective)	Roman Catholic (adjective)
of or relating to or supporting Romanism	of or relating to or supporting Romanism