Source : Webster's Revised Unabridged Dictionary (1913)

Double \Dou"ble\, v. t. [imp. & p. p. {Doubled}; p. pr. & vb. n.
   {Doubling}.] [OE. doblen, dublen, doublen, F. doubler, fr. L.
   duplare, fr. duplus. See {Double}, a.]
   1. To increase by adding an equal number, quantity, length,
      value, or the like; multiply by two; to double a sum of
      money; to double a number, or length.

            Double six thousand, and then treble that. --Shak.

   2. To make of two thicknesses or folds by turning or bending
      together in the middle; to fold one part upon another part
      of; as, to double the leaf of a book, and the like; to
      clinch, as the fist; -- often followed by up; as, to
      double up a sheet of paper or cloth.

Doubling \Dou"bling\, n.
   1. The act of one that doubles; a making double;
      reduplication; also, that which is doubled.

   2. A turning and winding; as, the doubling of a hunted hare;
      shift; trick; artifice. --Dryden.

   3. (Her.) The lining of the mantle borne about the shield or
      escutcheon.

   4. The process of redistilling spirits, to improve the
      strength and flavor.

   {Doubling a cape}, {promontory}, etc. (Naut.), sailing around
      or passing beyond a cape, promontory, etc.

Source : WordNet®

doubling
     n 1: increase by a factor of two; "doubling with a computer took
          no time at all"
     2: raising the stakes in a card game by a factor of 2; "I
        decided his double was a bluff" [syn: {double}]