jet fuel vs natural gas

jet fuel

noun
  • The fuel that powers a jet aircraft. 

  • kerosene 

  • Strong home-brewed alcoholic drink; moonshine. 

natural gas

noun
  • A mixture of gaseous hydrocarbons associated with petroleum deposits; mostly methane with smaller amounts of ethane, propane and butane; principally used as a fuel. 

How often have the words jet fuel and natural gas occurred in a corpus of books? (source: Google Ngram Viewer )