—adj. 1. fourfold; consisting of four parts: a quadruple alliance. 2. four times as great.
3. Music.having four beats to a measure.
—n. 1. a number, amount, etc., four times as great as another.
2. something, as a series of acrobatic somersaults, made up of four clearly defined parts or stages: the first trapeze artist to perform a quadruple successfully.
—v.t., v.i. to make or become four times as great: To serve 24 people, quadruple the recipe. My savings quadrupled in 20 years.