combustion

noun4

1. •
   The act or process of burning.
2. •
   A process whereby two chemicals are combined to produce heat.
3. •
   A process wherein a fuel is combined with oxygen, usually at high temperature, releasing heat.
4. •
   (figurative) Violent agitation, tumult.

   • There [were] great combustions and divisions among the heads of the university. — 1665