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]