1. designed or made so that it cannot fail or be used incorrectly; incapable of going wrong

Examples

• The new software has a foolproof backup system that automatically saves your work.
• This recipe is foolproof—even beginners can follow it successfully.
• The company designed a foolproof locking mechanism that prevents accidental opening.
• The instructions are so clear and foolproof that anyone can assemble the furniture.
• We need a foolproof plan before we launch the product to the market.
• The security system is foolproof and has never been breached.