Source : Webster's Revised Unabridged Dictionary (1913)

Unknot \Un*knot"\, v. t. [1st un- + knot.]
   To free from knots; to untie.

Source : WordNet®

unknot
     v : become or cause to become undone by separating the fibers or
         threads of; "the sweater unravelled" [syn: {unravel}, {unscramble},
          {untangle}, {unpick}] [ant: {ravel}, {ravel}]