The Collaborative International Dictionary of English v.0.48:

Ignition \Ig*ni"tion\, n. [Cf. F. ignition.]
   1. The act of igniting, kindling, or setting on fire.
      [1913 Webster]

   2. The state of being ignited or kindled. --Sir T. Browne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ignition
    n 1: the process of initiating combustion or catching fire
    2: the mechanism that ignites the fuel in an internal-combustion
       engine [syn: ignition, ignition system]
    3: the act of setting something on fire [syn: ignition,
       firing, lighting, kindling, inflammation]