Unutterable (9)
I believe the answer is:
ineffable
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unutterable</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ineffable that I've seen before include "Inexpressible" , "Too great to be put into words" , "beyond description" , "Indescribable in words" , "Beyond words" .)