motorcycle vs minibike

motorcycle and minibike both are nouns.

As nouns, minibike is a hyponym of motorcycle; that is, minibike is a word with a more specific, narrower meaning than motorcycle:

motorcycle: a motor vehicle with two wheels and a strong frame
minibike: small motorcycle with a low frame and small wheels and elevated handlebars

Other hyponyms of motorcycle include motorbike, dirt bike, scrambler, trail bike.

motorcycle (noun)	minibike (noun)
a motor vehicle with two wheels and a strong frame	small motorcycle with a low frame and small wheels and elevated handlebars

motorcycle (verb)	minibike (verb)
ride a motorcycle