Unspeakable
Part of speech: adjective
Definition: Incapable of being spoken or uttered; unutterable; ineffable; inexpressible. Unfit or not permitted to be spoken or described. Extremely bad or objectionable.
Example sentence: There's an effort to reclaim the unmentionable, the unsayable, the unspeakable, all those things come into being a composer, into writing music, into searching for notes and pieces of musical information that don't exist.
Ineffable
Part of speech: adjective
Definition: Beyond expression in words; unspeakable.Forbidden to be uttered; taboo.
Example sentence: She saw the myriad gods, and beyond God his own ineffable eternity; she saw that there were ranges of life beyond our present life, ranges of mind beyond our present mind and above these she saw the splendors of the spirit.