In'di-cā'tor, n.

n. [Lat., It. indicatore, Fr. indicateur.]

1. One who, or that which, shows or points out.
2. (Steam-eng.) An instrument by which the working steam records its working pressure, from which the power of the engine may be calculated. It consists of a small cylinder communicating by a cock with the cylinder of the engine, and fitted with a piston, to which a pencil is attached. The roller, upon which a card is fastened, is oscillated forward and backward by a cord attached to the piston-rod of the engine. As the pencil rises by the steam-pressure, and is brought back by a graduated spring when that pressure is reduced by expansion and condensation, a figure representing the pressure at each point in the stroke of the engine, is traced upon the card. See INDICATOR-CARD and HORSE-POWER.
3. A dynamometer for measuring the power of any prime mover.
4. (Ornith.) A genus of birds belonging to the tribe of the cuckoos; the honey-guides; — so called from their pointing out by their presence or movements the nests of bees. They are natives of South Africa. Baird.