combustion vs roar

combustion

noun
  • Violent agitation, tumult. 

  • A process wherein a fuel is combined with oxygen, usually at high temperature, releasing heat. 

  • A process whereby two chemicals are combined to produce heat. 

  • The act or process of burning. 

roar

noun
  • A long, loud, deep shout, as of rage or laughter, made with the mouth wide open. 

  • A loud resounding noise. 

  • A show of strength or character. 

  • The deep cry of the bull. 

  • The cry of the lion. 

verb
  • Of animals (especially a lion), to make a loud deep noise. 

  • To make a loud noise in breathing, as horses do when they have a certain disease. 

  • To proceed vigorously. 

  • To be boisterous; to be disorderly. 

  • Generally, of inanimate objects etc., to make a loud resounding noise. 

  • To cry aloud; to proclaim loudly. 

  • To laugh in a particularly loud manner. 

  • To make a loud, deep cry, especially from pain, anger, or other strong emotion. 

  • to cry 

How often have the words combustion and roar occurred in a corpus of books? (source: Google Ngram Viewer )