n. One who conducts or escorts; one who goes before or accompanies and shows the way; a leader; a guide.n. Specifically A chief; a commander; one who leads an army.n. A director or manager in general; a regulator.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.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.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.n. Hence A lightning-rod.n. In surgery, an instrument formerly used in the high operation for stone in the bladder.Specifically, in electricity, a substance through which electric currents can flow.