Source : Webster's Revised Unabridged Dictionary (1913)

Quadruple \Quad"ru*ple\, a. [L. quadruplus, from quattuor four:
   cf. F. quadruple. See {Quadrate}, and cf. {Double}.]
   Fourfold; as, to make quadruple restitution; a quadruple
   alliance.

   {Quadruple time} (Mus.), that in which each measure is
      divided into four equal parts.

Quadruple \Quad"ru*ple\, n. [Cf. F. quadruple, L. quadruplum.]
   four times the sum or number; a fourfold amount; as, to
   receive to quadruple of the amount in damages.

Quadruple \Quad"ru*ple\, v. t. [imp. & p. p. {Quadrupled}; p.
   pr. & vb. n. {Quadrupling}.] [L. quadruplare: cf. F.
   quadrupler.]
   To multiply by four; to increase fourfold; to double; to
   double twice. --A. Smith.

Quadruple \Quad"ru*ple\, v. i.
   To be multiplied by four; to increase fourfold; to become
   four times as much.

Source : WordNet®

quadruple
     adj 1: having four units or components; "quadruple rhythm has four
            beats per measure"; "quadruplex wire" [syn: {quadruplicate},
             {quadruplex}, {fourfold}]
     2: four times as great or many; "a fourfold increase in the
        dosage" [syn: {fourfold}]
     n : a quantity that is four times as great as another

quadruple
     v : increase fourfold; "His stock earning quadrupled"