secondhand car vs motorcar

secondhand car and motorcar both are nouns.

Word	Noun	Adjective	Verb	Adverb
secondhand car	Yes	No	No	No
motorcar	Yes	No	No	No

As nouns, motorcar is a hypernym of secondhand car; that is, motorcar is a word with a broader meaning than secondhand car:

secondhand car: a car that has been previously owned; not a new car
motorcar: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other hypernyms of secondhand car include auto, automobile, car, machine.

secondhand car (noun)	motorcar (noun)
a car that has been previously owned; not a new car	a motor vehicle with four wheels; usually propelled by an internal combustion engine