trackless trolley vs bus

trackless trolley and bus both are nouns.

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

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

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

trackless trolley (noun)	bus (noun)
a passenger bus with an electric motor that draws power from overhead wires	a vehicle carrying many passengers; used for public transport
	a car that is old and unreliable
	an electrical conductor that makes a common connection between several circuits
	the topology of a network whose components are connected by a busbar

trackless trolley (verb)	bus (verb)
	remove used dishes from the table in restaurants
	ride in a bus
	send or move around by bus