unpick

from WordNet (r) 3.0 (2006)

unpick
    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: undo (the stitches) of (a piece of sewing)

from The Collaborative International Dictionary of English v.0.48

Unpick \Un*pick\, v. t. [1st pref. un- (intensive) + pick.]
   To pick out; to undo by picking.
   [1913 Webster]