The Collaborative International Dictionary of English v.0.48:

Unravel \Un*rav"el\, v. t. [1st pref. un- (intensive) + ravel.]
   [1913 Webster]
   1. To disentangle; to disengage or separate the threads of;
      as, to unravel a stocking.
      [1913 Webster]

   2. Hence, to clear from complication or difficulty; to
      unfold; to solve; as, to unravel a plot.
      [1913 Webster]

   3. To separate the connected or united parts of; to throw
      into disorder; to confuse. "Art shall be conjured for it,
      and nature all unraveled." --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Unravel \Un*rav"el\, v. i.
   To become unraveled, in any sense.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unravel
    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]
    2: disentangle; "can you unravel the mystery?" [syn: ravel,
       unravel, ravel out] [ant: knot, ravel, tangle]
    3: become undone; "the sweater unraveled" [syn: run,
       unravel]

Moby Thesaurus II by Grady Ward, 1.0:

155 Moby Thesaurus words for "unravel":
   account for, allegorize, answer, avulse, bottom, break,
   break loose, break out, carry away, clarify, clear, clear up,
   come apart, come off, come undone, come unstuck, crack, crack up,
   cut loose, cut out, debug, decipher, decode, demonstrate,
   demythologize, deracinate, dig out, dig up, disembarrass,
   disembroil, disengage, disentangle, disintegrate, disintricate,
   disinvolve, dislodge, dissolve, divine, do, dope, dope out, draw,
   draw out, dredge, dredge up, elucidate, enlighten, eradicate,
   euhemerize, evolve, evulse, excavate, excise, exemplify, explain,
   explain away, explicate, exposit, expound, exsect, extract,
   extricate, fall off, fall to pieces, fathom, figure out, find out,
   find the answer, find the solution, fly apart, free, get,
   get loose, get out, get right, give reason for, give the meaning,
   give way, go to pieces, gouge out, grub up, guess, guess right,
   have it, hit it, illuminate, illustrate, interpret, make clear,
   make out, make plain, mine, open the lock, peel off, pick out,
   pluck out, pluck up, plumb, popularize, psych, psych out, pull,
   pull out, pull up, puzzle out, quarry, rake out, rationalize,
   ravel, ravel out, release, remove, resolve, riddle, rip out,
   root out, root up, shed light upon, show, show how, show the way,
   simplify, solve, sort out, spell out, spring apart, start,
   take out, tear loose, tear out, throw light upon, unbraid,
   unclutter, uncoil, undo, unearth, unfold, unknot, unlock, unmix,
   unriddle, unscramble, unsnarl, untangle, unthread, untwine,
   untwist, unweave, unwind, uproot, weed out, withdraw, work,
   work out, wrest out