Source : Webster's Revised Unabridged Dictionary (1913)

Ineffable \In*ef"fa*ble\, a. [L. ineffabilis: cf. F. ineffable.
   See {In-} not, and {Effable}, {Fame}.]
   Incapable of being expresses in words; unspeakable;
   unutterable; indescribable; as, the ineffable joys of heaven.

         Contentment with our lot . . . will diffuse ineffable
         contentment over the soul.               --Beattie.

Source : WordNet®

ineffable
     adj 1: defying expression or description; "indefinable yearnings";
            "indescribable beauty"; "ineffable ecstasy";
            "inexpressible anguish"; "unspeakable happiness";
            "unutterable contempt"; "a thing of untellable
            splendor" [syn: {indefinable}, {indescribable}, {unspeakable},
             {untellable}, {unutterable}]
     2: too sacred to be uttered; "the ineffable name of the Deity"
        [syn: {unnameable}, {unspeakable}, {unutterable}]