Meaning
A bus with two long poles on its roof connected to overhead electric wires. It is a trolleybus, an electric bus that runs on ordinary roads but draws power from cables above.
Use it for public transport in cities that still run them, for green-transport talk and for travel memories: “Rode an old 🚎 across town, the poles kept sparking”. It is often confused with a tram, but it runs on rubber tyres, not rails.