noun (n)

• a process in which a substance reacts with oxygen to give heat and light(noun.process)

  Synonym:
  burning
  

  source: wordnet30
• a state of violent disturbance and excitement(noun.state)

  Example:
  Combustion grew until revolt was unavoidable.
  

  source: wordnet30
• the act of burning something(noun.act)

  source: wordnet30
• The state of burning.(noun)

  source: webster1913