UK (US not be carved/etched in stone)
- to be able to be changed
- firmly established and very difficult to change = set in concrete
The schedule is not set in stone, but we'd like to stick to it pretty closely.
These are just a new ideas - nothing is set in stone.
Usage notes: sometimes with other verbs, such as write, carve, or etch:
Our business plan isn't carved in stone, we can still make adjustments if we need to.