Source : Webster's Revised Unabridged Dictionary (1913)

Combustion \Com*bus"tion\ (?; 106), n. [L. combustio: cf. F.
   combustion.]
   1. The state of burning.

   2. (Chem.) The combination of a combustible with a supporter
      of combustion, producing heat, and sometimes both light
      and heat.

            Combustion results in common cases from the mutual
            chemical action and reaction of the combustible and
            the oxygen of the atmosphere, whereby a new compound
            is formed.                            --Ure.

   {Supporter of combustion} (Chem.), a gas, as oxygen, the
      combination of which with a combustible, as coal,
      constitutes combustion.

   3. Violent agitation; confusion; tumult. [Obs.]

            There [were] great combustions and divisions among
            the heads of the university.          --Mede.

            But say from whence this new combustion springs.
                                                  --Dryden.

Source : WordNet®

combustion
     n 1: a process in which a substance reacts with oxygen to give
          heat and light [syn: {burning}]
     2: a state of violent disturbance and excitement; "combustion
        grew until revolt was unavoidable"
     3: the act of burning something; "the burning of leaves was
        prohibited by a town ordinance" [syn: {burning}]