Source : Webster's Revised Unabridged Dictionary (1913)

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.