black Maria vs paddy wagon

black Maria and paddy wagon both are nouns.

Word	Noun	Adjective	Verb	Adverb
black Maria	Yes	No	No	No
paddy wagon	Yes	No	No	No

As nouns, black Maria and paddy wagon are synonyms defined as:

Other synonyms of black Maria include patrol wagon, police van, police wagon, wagon.

black Maria (noun)	paddy wagon (noun)
van used by police to transport prisoners	van used by police to transport prisoners