Unspeakable
Vine's Expository Dictionary of NT Words [1]
denotes "inexpressible" (a, negative, n, euphonic, ekdiegeomai, "to declare, relate"), 2 Corinthians 9:15 , "unspeakable" (of the gift of God); regarding the various explanations of the gift, it seems most suitable to view it as the gift of His Son.
denotes "unable to be told out" (eklaleo, "to speak out"), 1 Peter 1:8 , of the believer's joy.
primarily, "unspoken" (a, negative, rhetos, "spoken"), denotes "unspeakable," 2 Corinthians 12:4 , of the words heard by Paul when caught up into paradise. The word is common in sacred inscriptions especially in connection with the Greek Mysteries; hence Moulton and Milligan suggest the meaning "words too sacred to be uttered."
King James Dictionary [2]
Unspe'Akable, a. That cannot be uttered that cannot be expressed unuterable as unspeakable grief or rage. 2 Corinthians 12 .
Joy unspeakable and full of glory. 1 Peter 1 .
Webster's Dictionary [3]
(a.) Not speakable; incapable of being uttered or adequately described; inexpressible; unutterable; ineffable; as, unspeakable grief or rage.