conductor

(noun): One who conducts or leads; a guide; a director.
(noun): A person who conducts an orchestra, choir or other music ensemble; a professional whose occupation is conducting.
(noun): A person who takes tickets on public transportation and also helps passengers
(noun): Something that can transmit electricity, heat, light or sound.
(noun): An ideal of a ring that measures how far it is from being integrally closed
(noun): A grooved sound or staff used for directing instruments, such as lithontriptic forceps; a director.
(noun): A leader.