ignition

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The raising of a substance to its ignition point, as by electric current, friction, or mechanical shock.
2. n. An electrical system, typically powered by a battery or magneto, that provides the spark to ignite the fuel mixture in an internal-combustion engine.
3. n. A switch that activates this system.

Century Dictionary and Cyclopedia

1. n. The act of igniting, kindling, or setting on fire.
2. n. Means of igniting; provision for firing.
3. n. The state of being ignited; a burning.
4. n. In chem., the process of roasting or intensely heating a substance.
5. n. In internal-combustion motors, the setting fire to the mixture of air and hydrocarbon vapor in the cylinder, so that the air shall expand and increase its pressure and perform the work required. Ignition is mainly effected, in modern motors, by an electric spark which jumps across a gap between terminals and in so doing raises the temperature of the mixture to the igniting-point. Such electric ignition may be by the jump-spark system, or by the make-and-break system. In the jump-spark system, the terminals on the secondary circuit of a Ruhmkorff or induction-coil are used. The current is made and broken on the primary or battery circuit, and this sends a secondary current of high intensity through the secondary line, in which are the gap-terminals. The primary make-and-break effect may be either by mechanical or by electrical vibrators, timed at will by the revolution of the motor-shaft. The hammer-break or arc system ignites by causing a flowing primary current to be mechanically interrupted by the separation of two contacts in the circuit. The current arcs across the break until the gap becomes too wide and the arc sets fire to the mixture around it. The make-and-break gives a ‘fat’ or copious spark, but considerable battery-power is needed; the jump-spark gives a tenuous high-tension spark, with less battery-power. Magneto-electric machines or small dynamos are much used for electric ignitions. Ignition may also be effected by compressing the mixture and at the right time allowing it to enter a hot tube of refractory material heated to redness by an exterior flame; or simple compression within the hot walls of the containing-chamber will fire an easily ignited mixture.

Wiktionary

1. n. The act of igniting.
2. n. The initiation of combustion.
3. n. A system for activating combustion in a combustion engine.

GNU Webster's 1913

1. n. The act of igniting, kindling, or setting on fire.
2. n. The state of being ignited or kindled.

WordNet 3.0

1. n. the process of initiating combustion or catching fire
2. n. the mechanism that ignites the fuel in an internal-combustion engine
3. n. the act of setting something on fire