Source : Webster's Revised Unabridged Dictionary (1913)

Unbrace \Un*brace"\, v. t. [1st pref. un- + brace.]
   To free from tension; to relax; to loose; as, to unbrace a
   drum; to unbrace the nerves. --Spenser.

Source : WordNet®

unbrace
     v 1: undo the ties of; "They untied the prisoner" [syn: {untie},
          {unlace}] [ant: {tie}]
     2: remove from tension
     3: remove a brace or braces from
     4: remove a brace or braces form