Source : Webster's Revised Unabridged Dictionary (1913)

Stiffening \Stiff"en*ing\, n.
   1. Act or process of making stiff.

   2. Something used to make anything stiff.

   {Stiffening order} (Com.), a permission granted by the
      customs department to take cargo or ballast on board
      before the old cargo is out, in order to steady the ship.