1. Too sacred to be uttered
   - ineffable, unnameable, unspeakable, unutterable 
2. Not capable of being said
   - unspeakable

See also: sacred

• Oreortyx picta palmeri
• Orestes
• Orff
• organ
• organ donor
• organ loft
• organ of Corti
• organ of hearing
• organ of speech
• organ pipe
• organ stop
• organ transplant
• organ-grinder
• organdie
• organdy
• organelle
• organic
• organic brain syndrome
• organic chemistry
• organic compound
• organic disorder
• organic evolution
• organic fertiliser
• organic fertilizer
• organic law