Unaccountable (adjective)

1. Not required or expected to give an explanation or justification for one's actions or decisions.
2. Not able to be explained or accounted for.
3. Not responsible or accountable to anyone for one's actions or decisions.

Origin:

Formed from the prefix 'un-' meaning 'not' and 'accountable' meaning 'liable to be called to account; responsible for one's actions or decisions.'.

Examples:

1. The new head of the department acted in an unaccountable manner, ignoring the opinions of his colleagues.
2. She was always unaccountable for her whereabouts, leaving her friends and family to worry about her safety.
3. His behavior was completely unaccountable and completely irrational, leaving everyone around him completely confused.
4. The disappearance of the funds remains unaccountable, and the police are still investigating.
5. The unaccountable delay caused by the bad weather was beyond their control.