1. music director of orchestra or choir: somebody in charge of an orchestra or choir who marks time and signals musicians or singers when and how to play or sing
2. transportation somebody who collects fares: an employee who takes money for tickets on a bus or streetcar
3. rail railroad employee in charge of passengers: a railroad employee who is in charge of a train and whose job is to check tickets, announce stops, and attend to passengers' needs and safety
4. physics something that conveys heat or electricity: a substance, body, or medium that allows heat, electricity, light, or sound to pass along it or through it. Metals are good conductors of heat because of the high concentration of free electrons they contain.
