minibike vs bike

minibike and bike both are nouns.

As nouns, bike is a hypernym of minibike; that is, bike is a word with a broader meaning than minibike:

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

Other hypernyms of minibike include motorcycle.

minibike (noun)	bike (noun)
small motorcycle with a low frame and small wheels and elevated handlebars	a motor vehicle with two wheels and a strong frame
	a wheeled vehicle that has two wheels and is moved by foot pedals

minibike (verb)	bike (verb)
	ride a bicycle