The Collaborative International Dictionary of English v.0.48:

Slough \Slough\, v. i. [imp. & p. p. Sloughed; p. pr. & vb. n.
   Sloughing.] (Med.)
   To form a slough; to separate in the form of dead matter from
   the living tissues; -- often used with off, or away; as, a
   sloughing ulcer; the dead tissues slough off slowly.
   [1913 Webster]