A trolley is an object with wheels that you use to transport heavy things such as shopping or luggage.

A trolley is a small table on wheels which is used for serving drinks or food.

A trolley is a bed on wheels for moving patients in hospital.

A trolley or trolley car is an electric vehicle for carrying people which travels on rails in the streets of a town.

If you say that someone is off their trolley, you mean that their ideas or behaviour are very strange.