French phrase
C'est inacceptable.
Meaning
That is unacceptable.
When to use it
Clearly expresses strong rejection or condemnation. It presents conduct or treatment as impossible to accept and has a fairly strong tone in everyday speech.
Example dialogue
Le plat est froid.
The dish is cold.
C'est inacceptable. Je vais en parler au chef.
That is unacceptable. I will talk to the chef.