tandem bicycle vs bicycle-built-for-two

tandem bicycle and bicycle-built-for-two both are nouns.

Word	Noun	Adjective	Verb	Adverb
tandem bicycle	Yes	No	No	No
bicycle-built-for-two	Yes	No	No	No

As nouns, tandem bicycle and bicycle-built-for-two are synonyms defined as:

tandem bicycle and bicycle-built-for-two: a bicycle with two sets of pedals and two seats

Other synonyms of tandem bicycle include tandem.

tandem bicycle (noun)	bicycle-built-for-two (noun)
a bicycle with two sets of pedals and two seats	a bicycle with two sets of pedals and two seats