1. not required to explain or justify one's actions; not answerable to anyone
Usage: formal; often used in legal or organizational contexts
2. not able to be explained or accounted for; inexplicable
Usage: less common than sense 1

Examples

• The nonaccountable officials made decisions without public oversight.
• Her nonaccountable behavior raised concerns among the board members.
• The company's nonaccountable spending practices led to an investigation.
• A nonaccountable power structure can lead to corruption.
• The nonaccountable gap in the budget remained a mystery.
• He felt frustrated by the nonaccountable nature of the process.