unacceptable

An unacceptable situation or behavior is one that can't be tolerated or allowed.

When we say something's unacceptable, we usually mean it's not okay to happen or be done. It could be a rule that someone breaks, like cheating on a test, or a way of treating others that's hurtful and wrong. For example, if you witness bullying at school, the behavior might be considered unacceptable because it harms and intimidates people. If someone's actions are causing problems and hurting those around them, we might say their behavior is unacceptable. In some cases, an action can be so bad or extreme that it's unacceptable in any situation – for instance, stealing money from someone who really needs it would generally be seen as unacceptable.

Note: Sometimes 'unacceptable' can be used in a formal context to describe something that doesn't meet certain standards or expectations, like a product that doesn't work properly. In this case, the word means not up to par or failing some requirements.