Source : Webster's Revised Unabridged Dictionary (1913)

Inexpressible \In`ex*press"i*ble\, a.
   Not capable of expression or utterance in language;
   ineffable; unspeakable; indescribable; unutterable; as,
   inexpressible grief or pleasure. ``Inexpressible grandeur.''
   --Blair.

         In orbs Of circuit inexpressible they stood. --Milton.

Source : WordNet®

inexpressible
     adj : defying expression [syn: {unexpressible}] [ant: {expressible}]