Source : Webster's Revised Unabridged Dictionary (1913)

Ostensible \Os*ten"si*ble\, a. [From L. ostensus, p. p. of
   ostendere to show, prop., to stretch out before; fr. prefix
   obs- (old form of ob-) + tendere to stretch. See {Tend}.]
   1. Capable of being shown; proper or intended to be shown.
      [R.] --Walpole.

   2. Shown; exhibited; declared; avowed; professed; apparent;
      -- often used as opposed to {real} or {actual}; as, an
      ostensible reason, motive, or aim. --D. Ramsay.

Source : WordNet®

ostensible
     adj 1: appearing as such but not necessarily so; "for all his
            apparent wealth he had no money to pay the rent"; "the
            committee investigated some apparent discrepancies";
            "the ostensible truth of their theories"; "his seeming
            honesty" [syn: {apparent(a)}, {seeming(a)}]
     2: represented or appearing as such; pretended; "His ostensible
        purpose was charity, his real goal popularity" [syn: {ostensive}]