Source : Webster's Revised Unabridged Dictionary (1913)

Inexcusable \In`ex*cus"a*ble\, a. [L. inexcusabilis: cf. F.
   inexcusable. See {Excuse}.]
   Not excusable; not admitting excuse or justification; as,
   inexcusable folly.

         Therefore thou art inexcusable, O man, whosoever thou
         art that judgest; for wherein thou judgest another,
         thou condemnest thyself; for thou that judgest doest
         the same things.                         --Rom. ii. 1.

Source : WordNet®

inexcusable
     adj 1: without excuse or justification [ant: {excusable}]
     2: not excusable [syn: {unforgivable}]