Source : Webster's Revised Unabridged Dictionary (1913)

Arguable \Ar"gu*a*ble\, a.
   Capable of being argued; admitting of debate.

Source : WordNet®

arguable
     adj 1: capable of being supported by argument
     2: open to argument or debate; "that is a moot question" [syn:
        {debatable}, {disputable}, {moot}]