conductor

Short definition from Wiktionary

Noun

1. 1
   One who conducts or leads; a guide; a director.
2. 2
   A person who conducts an orchestra, choir or other music ensemble; a professional whose occupation is conducting.
3. 3
   A person who takes tickets on public transportation and also helps passengers.
4. 4
   Something that can transmit electricity, heat, light, or sound.
5. 5
   An ideal of a ring that measures how far it is from being integrally closed
6. 6
   A grooved sound or staff used for directing instruments, such as lithontriptic forceps; a director.
7. 7
   A leader.