motorcycle policeman vs speed cop

motorcycle policeman and speed cop both are nouns.

Word	Noun	Adjective	Verb	Adverb
motorcycle policeman	Yes	No	No	No
speed cop	Yes	No	No	No

As nouns, motorcycle policeman and speed cop are synonyms defined as:

motorcycle policeman and speed cop: a policeman who rides a motorcycle (and who checks the speeds of motorists)

Other synonyms of motorcycle policeman include motorcycle cop.

motorcycle policeman (noun)	speed cop (noun)
a policeman who rides a motorcycle (and who checks the speeds of motorists)	a policeman who rides a motorcycle (and who checks the speeds of motorists)