1. No longer changeable
   "the agreement is not yet set in stone"
   - carved in stone

See also: unchangeable

• optical crown glass
• optical density
• optical device
• optical disc
• optical disk
• optical fiber
• optical fibre
• optical flint
• optical fusion
• optical glass
• optical illusion
• optical instrument
• optical lens
• optical maser
• optical opacity
• optical phenomenon
• optical prism
• optical pyrometer
• optical rotation
• Inverness
• inverse
• inverse cosecant
• inverse cosine
• inverse cotangent
• inverse function