The Collaborative International Dictionary of English v.0.48:

Cast-off \Cast"-off`\, a.
   Cast or laid aside; thrown away; discarded; as, cast-off
   clothes.

   Syn: discarded, junked, scrap(prenominal), waste.
        [1913 Webster]

WordNet (r) 3.0 (2006):

cast-off
    adj 1: thrown away; "wearing someone's cast-off clothes";
           "throwaway children living on the streets"; "salvaged
           some thrown-away furniture" [syn: cast-off(a),
           discarded, throwaway(a), thrown-away(a)]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "castoff":
   castaway, deep six, derelict, discard, discarding, disposal, dogie,
   dumping, elimination, flotsam, flotsam and jetsam, foundling,
   jetsam, jettison, junk, junking, lagan, orphan, refuse, reject,
   rejectamenta, rejection, removal, rubbish, scrapping, throwaway,
   trash, waif, waifs and strays, wastrel