WordNet sense 1 (the topology of a network whose components are connected by a busbar):

bus topology

WordNet sense 2 (an electrical conductor that makes a common connection between several circuits):

busbar

WordNet sense 3 (a car that is old and unreliable):

heap, jalopy

WordNet sense 4 (a vehicle carrying many passengers; used for public transport):

coach, double-decker, jitney, omnibus, autobus, charabanc, motorbus, motorcoach, passenger vehicle