the GNU version of the Collaborative International Dictionary of English
adj. Incapable of being uttered.
The Century Dictionary and Cyclopedia
That cannot be uttered or expressed in words; unutterable; inexpressible.
Word Usage
"He thought that the circumstances of each case depended upon "utterless facts"; and that it was practically impossible for a civil court to decide on a subject so delicate in its essence, and so imperceptible in its data."