trolleybus vs omnibus

trolleybus and omnibus both are nouns.

Word	Noun	Adjective	Verb	Adverb
trolleybus	Yes	No	No	No
omnibus	Yes	Yes	No	No

As nouns, omnibus is a hypernym of trolleybus; that is, omnibus is a word with a broader meaning than trolleybus:

trolleybus: 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 trolleybus include autobus, bus, charabanc, coach, double-decker, jitney, motorbus, motorcoach, passenger vehicle.

trolleybus (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

trolleybus (adjective)	omnibus (adjective)
	providing for many things at once