trackless trolley vs autobus

trackless trolley and autobus both are nouns.

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

As nouns, autobus is a hypernym of trackless trolley; that is, autobus 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
autobus: a vehicle carrying many passengers; used for public transport

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

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