fail-safe Synonyms

error failover airtight backup unpassable unfailing unerring trusty trustworthy tested sure steady confirmed foolproof be money in the bank as good as your word safety device tried and true surefire sure-fire idiot-proof fallback failsafe defectless steadfast stable secure device dependable covered confident complete checked certified certain buffer attested effective emergency safety safeguard safe reliable protection protected insurance infallible guaranteed flawless approved