1) Philosophical concept 
Ineffability is concerned with ideas that cannot or should not be expressed in spoken words (or language in general), often being in the form of a taboo or incomprehensible term. This property is commonly associated with philosophy, aspects of existence, and similar concepts that are inherently `too great`, complex, or abstract to be adequately .....
• (n.) The quality or state of being ineffable; ineffableness; unspeakableness.
In·ef`fa·bil'i·ty noun [ Latin ineffabilitas : confer French ineffabilité .] The quality or state of being ineffable; ineffableness; unspeakableness. 
ineffable, ineffability 1. Incapable of being expressed in words. 2. Too great, or extreme, to be expressed or described in words.