unknot

from WordNet (r) 3.0 (2006)

unknot
    v 1: become or cause to become undone by separating the fibers
         or threads of; "unravel the thread" [syn: {unravel},
         {unknot}, {unscramble}, {untangle}, {unpick}] [ant: {knot},
         {ravel}, {tangle}]

from The Collaborative International Dictionary of English v.0.48

Unknot \Un*knot"\, v. t. [1st un- + knot.]
   To free from knots; to untie.
   [1913 Webster]