Not capable of being translated; also, not fit to be translated.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. not capable of being put into another form or style or language
Word Usage
"The Kalakistan Fragment, supposedly untranslatable, is thought to detail the life of Gung the Magnificent who nearly conquered the world in 1932 B.C. using “supernatural powers derived from a fabulous melon-size jewel.”"