The Collaborative International Dictionary of English v.0.48:

Combustible \Com*bus"ti*ble\, a. [Cf. F. combustible.]
   1. Capable of taking fire and burning; apt to catch fire;
      inflammable.
      [1913 Webster]

            Sin is to the soul like fire to combustible matter.
                                                  --South.
      [1913 Webster]

   2. Easily kindled or excited; quick; fiery; irascible.
      [1913 Webster]

            Arnold was a combustible character.   --W. Irving.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Combustible \Com*bus"ti*ble\, n.
   A substance that may be set on fire, or which is liable to
   take fire and burn.
   [1913 Webster]

         All such combustibles as are cheap enough for common
         use go under the name of fuel.           --Ure.
   [1913 Webster]

WordNet (r) 3.0 (2006):

combustible
    adj 1: capable of igniting and burning [ant: incombustible,
           noncombustible]
    n 1: a substance that can be burned to provide heat or power
         [syn: combustible, combustible material]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "combustible":
   accendible, alcohol, benzine, briquette, burnable, butane, carbon,
   charcoal, coal, coke, dope, ethane, ethanol, explosive, fiery,
   fireball, firing, flammable, flammable material, fuel,
   fuel additive, fuel dope, gas, gas carbon, gasoline, hasty,
   heptane, hexane, hot, hot-tempered, hotheaded, inflammable,
   inflammable material, isooctane, jet fuel, kerosene, methane,
   methanol, natural gas, octane, oil, paraffin, passionate, peat,
   pentane, peppery, propane, propellant, quick, quick-tempered,
   rocket fuel, short-tempered, spunky, turf, volcanic