fail-safe; foolproof; totally safe
Describes a system, method, or situation that is designed to be completely safe and free from risk of failure or harm. Often used in technical, engineering, or everyday contexts to emphasize absolute reliability.
This system is designed to be fail-safe.
Please save the data in a foolproof way.
Compound of 絶対 (ぜったい, 'absolute') and 安全 (あんぜん, 'safety'). The combination straightforwardly yields the meaning 'absolute safety'.