Source : Webster's Revised Unabridged Dictionary (1913)

Justifiable \Jus"ti*fi`a*ble\, a. [Cf. F. justifiable. See
   {Justify}.]
   Capable of being justified, or shown to be just.

         Just are the ways of God, An justifiable to men.
                                                  --Milton.

   Syn: Defensible; vindicable; warrantable; excusable;
        exculpable; authorizable. -- {Jus"ti*fi`a*ble*ness}, n.
        -- {Jus"ti*fi`a*bly}, adv.

Source : WordNet®

justifiably
     adv : with good reason; "he is justifiably bitter" [syn: {with
           reason}] [ant: {unjustifiably}]