The Collaborative International Dictionary of English v.0.48:

Unwind \Un*wind"\, v. i.
   To be or become unwound; to be capable of being unwound or
   untwisted.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Unwind \Un*wind"\, v. t. [AS. unwindan. See 1st Un-, and
   Wind to coil.]
   [1913 Webster]
   1. To wind off; to loose or separate, as what or convolved;
      to untwist; to untwine; as, to unwind thread; to unwind a
      ball of yarn.
      [1913 Webster]

   2. To disentangle. [Obs.] --Hooker.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unwind
    v 1: reverse the winding or twisting of; "unwind a ball of yarn"
         [syn: unwind, wind off, unroll] [ant: roll,
         twine, wind, wrap]
    2: separate the tangles of [syn: unwind, disentangle]
    3: become less tense, rest, or take one's ease; "He relaxed in
       the hot tub"; "Let's all relax after a hard day's work" [syn:
       relax, loosen up, unbend, unwind, decompress, slow
       down] [ant: tense, tense up]
    4: cause to feel relaxed; "A hot bath always relaxes me" [syn:
       relax, unstrain, unlax, loosen up, unwind, make
       relaxed] [ant: strain, tense, tense up]