Four times as great or many:
— A fourfold increase in the dosage.

synonyms: four-fold, quadruple.

Polish: czterokrotny, poczwórny

Having four units or components.

synonyms: four-fold, quadruple, quadruplex, quadruplicate.

Roget 96: fourfold, four times; quadrable^†, quadrumanous^†, quadruple, quadruplicate, quadrible^†; fourth.    quadrifoliate^†, quadrifoliolate^†, quadrigeminal^†, quadrigeminate^†, quadriplanar^†, quadriserial^†.    ... show more

By a factor of four:
— The price of gasoline has increased fourfold over the past two years.

synonym: four times.