Unacceptable (adjective)

1. Not capable of being accepted; not satisfactory; not adequate.
2. Not conforming to approved or accepted standards, norms or rules.

Origin:

From un- "not" + acceptable, from the verb accept.

Examples:

1. This behavior is unacceptable in any workplace.
2. The company's response to the crisis was unacceptable.
3. His apology was unacceptable because it was insincere.
4. The quality of the work was unacceptable and had to be redone.
5. The terms of the contract are unacceptable, we will not sign it.