two-seater vs motorcar

two-seater and motorcar both are nouns.

Word	Noun	Adjective	Verb	Adverb
two-seater	Yes	No	No	No
motorcar	Yes	No	No	No

As nouns, motorcar is a hypernym of two-seater; that is, motorcar is a word with a broader meaning than two-seater:

two-seater: an open automobile having a front seat and a rumble seat
motorcar: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other hypernyms of two-seater include auto, automobile, car, machine.

two-seater (noun)	motorcar (noun)
an open automobile having a front seat and a rumble seat	a motor vehicle with four wheels; usually propelled by an internal combustion engine