Unaccountable means not having to explain your actions or decisions to anyone. When someone is unaccountable, they can do what they want without facing consequences or answering questions about their choices.

A king in medieval times was largely unaccountable: he could make laws, raise taxes, or start wars without needing permission or having to justify his decisions to his subjects. In contrast, a president in a democracy must answer to voters, courts, and legislatures. A teacher is accountable to the principal and to parents, while students are accountable to teachers for completing their homework.

Sometimes unaccountable describes a person or organization that operates without oversight. If a powerful company seems unaccountable, people might worry that it can ignore complaints or harm people without facing consequences. When citizens say their government officials should be accountable, they mean those officials should have to explain their decisions and face consequences for bad choices.

The word can also mean something impossible to explain or understand. A scientist might call a strange result unaccountable if nothing seems to explain why it happened. If your normally reliable friend acts strangely for unaccountable reasons, you can't figure out what's causing the behavior.