Source : Webster's Revised Unabridged Dictionary (1913)

Ravel \Rav"el\, v. t. [imp. & p. p. {Raveled}or {Ravelled}; p.
   pr. & vb. n. {Raveling} or {Ravelling}.] [. ravelen, D.
   rafelen, akin to LG. rebeln, rebbeln, reffeln.]
   1. To separate or undo the texture of; to take apart; to
      untwist; to unweave or unknit; -- often followed by out;
      as, to ravel a twist; to ravel out a sticking.

Source : WordNet®

ravelling
     n : a bit of fiber that has become separated from woven fabric
         [syn: {raveling}]

ravel
     v 1: disentangle; "can you unravel the mystery?"; "unravel the
          ball or yarn" [syn: {unravel}, {ravel out}]
     2: tangle or complicate; "a ravelled story" [syn: {tangle}, {knot}]
        [ant: {unravel}, {unravel}]
     [also: {ravelling}, {ravelled}]

ravelling
     See {ravel}