unsayable

adjective2

1. •
   Not capable of being said.

   • Nonetheless, in some unsayable way, value sentences are about values and reflect the structure of values. — 1938
2. •
   Not allowed or not fit to be said.

   • His task: to say the unsayable. To say all the words we have normally suppressed and to say them and say them and say them. — 1971