Source : Webster's Revised Unabridged Dictionary (1913)

Unconstraint \Un`con*straint"\, n.
   Freedom from constraint; ease. --Felton.

Source : WordNet®

unconstraint
     n : the trait of lacking restraint or control; freedom from
         inhibition or worry; "she danced with abandon" [syn: {abandon},
          {wantonness}]