popish vs Romanist

popish and Romanist both are adjectives.

Word	Noun	Adjective	Verb	Adverb
popish	No	Yes	No	No
Romanist	No	Yes	No	No

As adjectives, popish and Romanist are synonyms defined as:

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

popish (adjective)	Romanist (adjective)
of or relating to or supporting Romanism	of or relating to or supporting Romanism