autobus vs motorbus

autobus and motorbus both are nouns.

Word	Noun	Adjective	Verb	Adverb
autobus	Yes	No	No	No
motorbus	Yes	No	No	No

As nouns, autobus and motorbus are synonyms defined as:

autobus and motorbus: a vehicle carrying many passengers; used for public transport

Other synonyms of autobus include bus, charabanc, coach, double-decker, jitney, motorcoach, omnibus, passenger vehicle.

autobus (noun)	motorbus (noun)
a vehicle carrying many passengers; used for public transport	a vehicle carrying many passengers; used for public transport