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]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "unwind":
   calm down, clarify, clear up, collect oneself, compose oneself,
   cool it, cool off, disembroil, disentangle, disintricate,
   disinvolve, ease, ease off, ease up, get organized, let down,
   let up, let up on, loosen up, ravel, relax, simmer down, slack,
   slack off, slack up, slacken, slow down, sober down, sort out,
   take it easy, unbend, unbraid, unclutter, uncoil, unfold, unfurl,
   unknot, unlax, unmix, unravel, unreel, unroll, unscramble, unsnarl,
   untangle, unthread, untwine, untwist, unweave