Source : Webster's Revised Unabridged Dictionary (1913)

Ineffably \In*ef"fa*bly\, adv.
   In a manner not to be expressed in words; unspeakably.
   --Milton.

Source : WordNet®

ineffably
     adv : to an inexpressible degree; "she was looking very young
           tonight, and, as usual, indescribably beautiful, in a
           simple strapless dress of a green and white silky
           cotton" [syn: {indescribably}, {unutterably}, {unspeakably}]