What is the meaning of fourfold?

adjective

• Four times as great or many.
  • usage: "a fourfold increase in the dosage"
  • synonyms: quadruple, four-fold
• Having four units or components.
  • usage: "quadruple rhythm has four beats per measure"; "quadruplex wire"
  • synonyms: quadruple, quadruplicate, quadruplex, four-fold

adverb

• By a factor of four.
  • usage: "the price of gasoline has increased fourfold over the past two years"
  • synonyms: four times