The Collaborative International Dictionary of English v.0.48:

Dispensable \Dis*pen"sa*ble\, a. [LL. dispensabilis. See
   Dispense.]
   1. Capable of being dispensed or administered.
      [1913 Webster]

   2. Capable of being dispensed with. --Coleridge.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dispensable
    adj 1: capable of being dispensed with or done without;
           "dispensable items of personal property" [ant:
           indispensable]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "dispensable":
   admissible, allocated, allowable, apportionable, apportioned,
   back-burner, condonable, de trop, defensible, dinky, disposable,
   distributable, divisible, excess, excusable, exemptible,
   expendable, expiable, expletive, forgivable, gratuitous,
   immaterial, in excess, inappreciable, inconsequential,
   inconsiderable, inessential, inferior, inoffensive, insignificant,
   irrelevant, justifiable, legitimate, little, minor, minute,
   needless, negligible, nonessential, not vital, parceled,
   pardonable, petit, pleonastic, portioned out, prolix, reasonable,
   redundant, remissible, severable, small, spare, supererogatory,
   superfluous, tautologic, tautologous, technical, to spare,
   uncalled-for, unessential, unimpressive, unnecessary, unneeded,
   unnoteworthy, unobjectionable, useless, venial, verbose,
   vindicable, warrantable