foolproof

[fool-proof]

adjective

1. involving no risk or harm, even when tampered with.

2. never-failing.

   a foolproof method.

foolproof

/ ˈfuːlˌpruːf /

adjective

1. proof against failure; infallible

   a foolproof idea

2. (esp of machines) proof against human misuse, error, etc

Word History and Origins

Origin of foolproof¹

An Americanism dating back to 1900–05; fool ¹ + -proof

Example Sentences

“You can’t assume that something like that is going to be foolproof and nothing can happen.”

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Jenn’s date nights with her girlfriend always revolve around food — and her lipstick is foolproof.

Read more on Los Angeles Times

You might wonder how these products work and whether they're foolproof enough to put the fear of bleeding through your clothes at bay.

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As suppliers scramble to call new vendors or reroute supply lines, it’s clear that no one has a foolproof plan.

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But there is one foolproof sign that groundwater is disappearing: The earth above it collapses as the ground compresses like a drying sponge.

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Related Words

• flawless 
• reliable 
• surefire 
• unassailable