quadruple

(noun) a set of four similar things considered as a unit. Synonyms: quartet, quartette, quadruplet.

(noun) a quantity that is four times as great as another.

(verb) increase fourfold. Example: "His stock earning quadrupled."

(adj) having four units or components. Synonyms: quadruplicate, quadruplex, fourfold, four-fold. Examples: "Quadruple rhythm has four beats per measure." "Quadruplex wire."

(adj) four times as great or many. Synonyms: fourfold, four-fold. Example: "A fourfold increase in the dosage."