1. impossible to answer or respond to adequately
2. impossible to argue against or refute

Examples

• The philosopher posed an unanswerable question about the nature of existence.
• Her argument was unanswerable, leaving her opponents speechless.
• The mystery remains unanswerable despite years of investigation.
• He presented unanswerable evidence of the company’s wrongdoing.
• The riddle seemed unanswerable until someone found the clever solution.
• The critic’s unanswerable logic demolished the author’s thesis.
• Some questions about the universe may be forever unanswerable.