wagon vs black Maria

wagon and black Maria both are nouns.

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

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

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

wagon (noun)	black Maria (noun)
any of various kinds of wheeled vehicles drawn by an animal or a tractor	van used by police to transport prisoners
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