Unintentional (adjective)

1. Not done on purpose; not intentional.
2. Not deliberate or intended.

Origin:

Un + intentional.

Examples:

1. He apologized for the unintentional offense.
2. The unintentional mistake cost the company a lot of money.
3. He made an unintentional error on the test.
4. The injury was unintentional and he was not at fault.
5. She had an unintentional slip of the tongue and revealed a secret.