French phrase
Non, ce n'est pas acceptable.
Meaning
No, that is not acceptable.
When to use it
A firm way to reject a proposal or request. It is somewhat formal and can sound blunt.
Example dialogue
Non, ce n'est pas acceptable.
No, that is not acceptable.
D'accord, pardon. Que proposes-tu comme alternative ?
All right, sorry. What do you propose as an alternative?