言語道断
gon.go.dou.dan

Literally: say – language – road – sever

Alternately: Outrageous; scandalous; inexcusable; absurd; unreasonable; terrible; something so far beyond the pale that you don’t even have words to describe how crazy it is. Mostly used for bad things.

Notes: This compound comes to us from a Buddhist phrase in the Vimalakirti Sutra (維摩経, Yuimakyou) pointing to the impossibility of explaining Enlightenment using mere words; the insufficiency of language to describe higher reality.

There exists a commonly-used homonym to the first half of this compound in the form of 言語 (gengo), “language,” but in this compound the characters can only be read as gongo. Similarly, while some people write the latter half as homophone 同断, this is considered an error, because 同 (“the same”) makes no sense in context, while 道 refers to the act of expressing something with words.

Also the name of an apparently crappy and short-lived culture mag.