trackless trolley vs motorbus

trackless trolley and motorbus both are nouns.

Word	Noun	Adjective	Verb	Adverb
trackless trolley	Yes	No	No	No
motorbus	Yes	No	No	No

As nouns, motorbus is a hypernym of trackless trolley; that is, motorbus is a word with a broader meaning than trackless trolley:

trackless trolley: a passenger bus with an electric motor that draws power from overhead wires
motorbus: a vehicle carrying many passengers; used for public transport

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

trackless trolley (noun)	motorbus (noun)
a passenger bus with an electric motor that draws power from overhead wires	a vehicle carrying many passengers; used for public transport