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]

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "ignition":
   altitude peak, automatic control, backfire, balefire, beacon,
   beacon fire, blast-off, blaze, bonfire, burn, burning ghat,
   burnout, campfire, ceiling, cheerful fire, combustion,
   conflagration, corposant, cozy fire, crackling fire, crematory,
   death fire, descent, end of burning, fen fire, fire, firing, flame,
   flammation, flashing point, flicker, flickering flame, flight,
   forest fire, fox fire, funeral pyre, ignis fatuus, impact,
   inflammation, ingle, kindling, lambent flame, launch, lift-off,
   lighting, lighting up, marshfire, open fire, prairie fire, pyre,
   raging fire, rocket launching, sea of flames, sheet of fire, shoot,
   shot, signal beacon, smudge fire, three-alarm fire, trajectory,
   two-alarm fire, velocity peak, watch fire, wildfire, witch fire