quad·ru·ple / kwäˈdroōpəl/ • adj. consisting of four parts or elements: a quadruple murder. ∎  consisting of four times as much or as many as usual: a quadruple vodka. ∎  (of time in music) having four beats in a bar.• v. increase or be increased fourfold: [intr.] oil prices quadrupled in the 1970s. • n. a quadruple thing, number, or amount.DERIVATIVES: quad·ru·ply / -p(ə)lē/ adv.

quadruple fourfold. XVI. — (O)F — L. quadruplus; see QUADRU-, DUPLE.
So vb. XIV. — F. or late L. quadruplicate adj. and vb. XVII. — L. quadruplication XVI. — late L. quadruplet one of four at a birth. XVIII; after triplet.