conductor

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One who conducts, especially:
2. n. One who is in charge of a railroad train, bus, or streetcar.
3. n. Music One who directs an orchestra or other such group.
4. n. Physics A substance or medium that conducts heat, light, sound, or especially an electric charge.
5. n. A lightning rod, as on a house or barn.

Century Dictionary and Cyclopedia

1. n. One who conducts or escorts; one who goes before or accompanies and shows the way; a leader; a guide.
2. n. Specifically A chief; a commander; one who leads an army.
3. n. A director or manager in general; a regulator.
4. n. The director of a chorus or an orchestra; one who indicates to the performers the rhythm and the expression of a piece of concerted music by means of motions of the hands or of a baton. The office of conductor in the modern sense was not clearly distinguished from that of leader until about 1800; formerly the leader played an instrument, usually the harpsichord.
5. n. The chief official on a railroad-train, who directs, and is responsible for the execution of orders concerning, the movements of the train, and usually collects tickets or fares; hence, one who performs similar duties on a street-car, etc. The duties of the guard on European railways are similar, but less comprehensive.
6. n. That which conducts or transmits in any manner; specifically, in physics, a body that conducts or transmits through its substance energy in any of its forms: as, metals are conductors of electricity and of heat; water is a good conductor of sound. See conductivity.
7. n. Hence A lightning-rod.
8. n. In surgery, an instrument formerly used in the high operation for stone in the bladder.
9. Specifically, in electricity, a substance through which electric currents can flow. Metals are the best conductors; glass, rubber, air, etc., are very poor conductors. The following divisions may be made: Conductors of the first class, or metallic conductors, as the metals, carbon, silicon, etc., which, except that they are heated, are not affected by the current.

Wiktionary

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

GNU Webster's 1913

1. n. One who, or that which, conducts; a leader; a commander; a guide; a manager; a director.
2. n. United States One in charge of a public conveyance, as of a railroad train or a street car.
3. n. (Mus.) The leader or director of an orchestra or chorus.
4. n. (Physics) A substance or body capable of being a medium for the transmission of certain forces, esp. heat or electricity; specifically, a lightning rod.
5. n. (Surg.) A grooved sound or staff used for directing instruments, as lithontriptic forceps, etc.; a director.
6. n. (Arch.) Same as Leader.

WordNet 3.0

1. n. a substance that readily conducts e.g. electricity and heat
2. n. the person who leads a musical group
3. n. a device designed to transmit electricity, heat, etc.
4. n. the person who collects fares on a public conveyance