foolproof

adjective

fool·​proof ˈfül-ˌprüf 

: so simple, plain, or reliable as to leave no opportunity for error, misuse, or failure

a foolproof plan

Examples of foolproof in a Sentence

DNA fingerprinting gives police a virtually foolproof way to link a suspect to a crime scene.

Recent Examples on the Web

However, essential oils are best used as a preventative measure, not a foolproof solution against wasps, says Rick Young, owner of Youngs Pest Control. —Louise Parks, Martha Stewart, 21 June 2026

Although computer spell-check is quite reliable, nothing is absolutely foolproof. —Jeanne Phillips, Mercury News, 20 June 2026

This all sounds impressive enough, but even futuristic weapons like lasers are not foolproof on the battlefield. —Christopher McFadden, Interesting Engineering, 20 June 2026

Matching sets are always a foolproof way to instantly put together, and this guest's coordinating pink denim proves the point. —Amanda Le, InStyle, 20 June 2026

Word History

First Known Use

1874, in the meaning defined above

Rhymes for foolproof

• aloof
• behoof
• disproof
• flameproof
• greaseproof
• leakproof
• reproof
• soundproof
• bulletproof
• fireproof
• waterproof
• weatherproof

Kids Definition

foolproof

adjective

fool·​proof ˈfül-ˈprüf 

: done, made, or planned so well that nothing can go wrong

foolproof directions