Source : Webster's Revised Unabridged Dictionary (1913)

Slowness \Slow"ness\, n.
   The quality or state of being slow.

Source : WordNet®

slowness
     n 1: unskillfulness resulting from a lack of training [syn: {awkwardness},
           {clumsiness}, {ineptness}, {ineptitude}, {maladroitness}]
     2: a rate demonstrating an absence of haste or hurry [syn: {deliberation},
         {deliberateness}, {unhurriedness}]
     3: lack of normal development of intellectual capacities [syn:
        {retardation}, {mental retardation}, {backwardness}, {subnormality}]