trol·ley / ˈträlē/ • n. (pl. -leys) 1. short for trolley car or trolley bus.2. (also trolley wheel) a wheel attached to a pole, used for collecting current from an overhead electric wire to drive a streetcar or trolley bus.3. a large metal basket or frame on wheels, resembling a shopping cart and used for transporting luggage at an airport or railroad station; a luggage cart. ∎ Brit. a shopping cart. ∎  Brit. a small table on wheels or casters, typically used to convey food and drink.4. chiefly Brit. a low truck, usually without sides or ends, running on a railroad or a track in a factory.PHRASES: off one's trolley inf. mad; insane.

trolley XIX. Presumably f. TROLL1; *dial. troll (XVII).