not permitted; not allowed; unacceptable
Formal or technical term for something that is not permitted or not acceptable, often used in rules, specifications, or system settings.
This operation is not permitted.
Unacceptable characters are included.
許容 means 'permissible' or 'allowable'; 非許容 is its direct negation.
Compound of 非 (hi, 'non-') and 許容 (kyoyō, 'permission, allowance').