black Maria vs wagon

black Maria and wagon both are nouns.

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

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

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

black Maria (noun)	wagon (noun)
van used by police to transport prisoners	any of various kinds of wheeled vehicles drawn by an animal or a tractor
	a car that has a long body and rear door with space behind rear seat
	van used by police to transport prisoners
	a child's four-wheeled toy cart sometimes used for coasting