trackless trolley vs omnibus

trackless trolley and omnibus both are nouns.

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

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

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

trackless trolley (noun)	omnibus (noun)
a passenger bus with an electric motor that draws power from overhead wires	a vehicle carrying many passengers; used for public transport
	an anthology of articles on a related subject or an anthology of the works of a single author

trackless trolley (adjective)	omnibus (adjective)
	providing for many things at once