Source : Webster's Revised Unabridged Dictionary (1913)

Swiftness \Swift"ness\, n.
   The quality or state of being swift; speed; quickness;
   celerity; velocity; rapidity; as, the swiftness of a bird;
   the swiftness of a stream; swiftness of descent in a falling
   body; swiftness of thought, etc.

Source : WordNet®

swiftness
     n : a rate (usually rapid) at which something happens; "the
         project advanced with gratifying speed" [syn: {speed}, {fastness}]