1. Noun. A set of four similar things considered as a unit.

Generic synonyms: Set

2. Verb. Increase fourfold. "Their earnings quadruple this year"; "His stock earning quadrupled"
Generic synonyms: Manifold, Multiply

Similar to: Multiple

4. Noun. A quantity that is four times as great as another.
Generic synonyms: Multiple

5. Adjective. Four times as great or many. "A fourfold increase in the dosage"
Exact synonyms: Four-fold, Fourfold
Similar to: Multiple

2. n. four times the sum or number; a fourfold amount; as, to receive to quadruple of the amount in damages.

3. v. t. To multiply by four; to increase fourfold; to double; to double twice.

4. v. i. To be multiplied by four; to increase fourfold; to become four times as much.

1. Adjective. Being four times as long, as big or as many of something. ¹

2. Verb. To multiply something by four times. ¹

¹ Source: wiktionary.com

1. [v -PLED, -PLING, -PLES]

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Below you will find example usage of this term as found in modern and/or classical literature:

1. A Treatise on Universal Algebra: With Applications by Alfred North Whitehead (1898)
"(2) Also the common null lines of a dual group are the lines intersecting the two director lines of the group; and the director lines of a quadruple ..."

2. The History of England from the Accession of Anne to the Death of George II by Isaac Saunders Leadam (1909)
"a8o THE quadruple ALLIANCE. 1717 CHAP, woolsack. The strength of the whig ascendancy was shewn XVI" by the fact that the party could furnish this strong ..."

3. Elements of International Law by Henry Wheaton (1904)
"The quadruple alliance, concluded in 1831 between quadruple France, Great Britain, Spain, and Portugal, affords a remarkable example of actual interference ..."

4. Encyclopædia Americana: A Popular Dictionary of Arts, Sciences, Literature by Thomas Gamaliel Bradford (1835)
"quadruple and QUINTUPLE ALLIANCE*. The natural, but undue influence, which European states have mutually exercised upon each other, has at times produced ..."

5. A History of Diplomacy in the International Development of Europe by David Jayne Hill (1914)
"V AD 1715-1731 Dissolution of the quadruple Alliance policy, ... The definite end for which the quadruple Alliance had been formed having been accomplished, ..."

6. Report of the Annual Meeting (1880)
"On Plane and Spherical Curves of the Fourth Class with quadruple Foci. ... All quartics with quadruple foci may be expressed by the geometrical relation xp* ..."

7. Encyclopaedia Americana: A Popular Dictionary of Arts, Sciences, Literature by Francis Lieber, Thomas Gamaliel Bradford (1832)
"The quadruple alliance of Austria, Russia, Great Britain, and Prussia, ... History will yet speak of quadruple and quintuple alliances in the great struggle ..."