The Collaborative International Dictionary of English v.0.48:

throwaway \throw"a*way\ a.
   1. designed to be discarded after a single use; disposable.
      [PJC]

   2. spoken with deliberate underemphasis; as, a throwaway line
      in a play.
      [PJC]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

throwaway \throw"a*way\ n.
   1. an advertisement (usually printed on a page or in a
      leaflet) intended for wide distribution.

   Syn: circular, handbill, bill, broadside, broadsheet, flier,
        flyer
        [WordNet 1.5]

   2. words spoken in a casual way with conscious underemphasis.
      [WordNet 1.5]
      [1913 Webster]

WordNet (r) 3.0 (2006):

throwaway
    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)]
    2: intended to be thrown away after use; "throwaway diapers"
    n 1: (sometimes offensive) a homeless boy who has been abandoned
         and roams the streets [syn: street arab, gamin,
         throwaway]
    2: an advertisement (usually printed on a page or in a leaflet)
       intended for wide distribution; "he mailed the circular to
       all subscribers" [syn: circular, handbill, bill,
       broadside, broadsheet, flier, flyer, throwaway]
    3: words spoken in a casual way with conscious under-emphasis

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "throwaway":
   castaway, castoff, consumable, deep six, discard, discarding,
   disposable, disposal, dumping, elimination, expendable, jettison,
   junking, no-deposit, refuse, reject, rejectamenta, rejection,
   removal, replaceable, scrapping, spendable