Source : Webster's Revised Unabridged Dictionary (1913)

Double \Dou"ble\, v. i.
   1. To be increased to twice the sum, number, quantity,
      length, or value; to increase or grow to twice as much.

            'T is observed in particular nations, that within
            the space of three hundred years, notwithstanding
            all casualties, the number of men doubles. --T.
                                                  Burnet.

   2. To return upon one's track; to turn and go back over the
      same ground, or in an opposite direction.

            Doubling and turning like a hunted hare. --Dryden.

            Doubling and doubling with laborious walk.
                                                  --Wordsworth.

   3. To play tricks; to use sleights; to play false.

            What penalty and danger you accrue, If you be found
            to double.                            --J. Webster.

   4. (Print.) To set up a word or words a second time by
      mistake; to make a doublet.

   {To double upon} (Mil.), to inclose between two fires.