Source : Webster's Revised Unabridged Dictionary (1913)

Presumable \Pre*sum"a*ble\, a. [Cf. F. pr['e]sumable.]
   Such as may be presumed or supposed to be true; that seems
   entitled to belief without direct evidence.

Source : WordNet®

presumable
     adj : able to be inferred on slight grounds [syn: {supposable}, {surmisable}]