1. Too sacred to be uttered
   - ineffable, unspeakable, unutterable, unsayable

See also: sacred

• substantively
• substantivise
• substantivize
• substation
• substituent
• substitutability
• substitutable
• substitute
• substitute teacher
• substituting
• substitution
• substitution class
• substitutional
• substitutionary
• substitutive
• substract
• substrate
• substratum
• substring
• substructure
• subsume
• subsumption
• subsurface
• subsystem
• subtenant