foolproof
Americanadjective
-
involving no risk or harm, even when tampered with.
-
never-failing.
a foolproof method.
adjective
-
proof against failure; infallible
a foolproof idea
-
(esp of machines) proof against human misuse, error, etc
Etymology
Origin of foolproof
Explanation
When something is bound to work out, you can call it foolproof. Your foolproof plan for having a great summer might involve spending lots of time at the beach. If your dog tends to wander and can also jump six feet in the air, a foolproof plan for keeping her in your yard might involve an eight foot fence. You can also use foolproof as a verb: "I'm going to foolproof the instructions for heating up your dinner, so that no one sets the stove on fire this time." Foolproof is an early twentieth century American English word that combines fool, or "silly person" and proof, "resistant."
Vocabulary lists containing foolproof
Game Changer
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Old Yeller
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The Bad Beginning
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
For the people on your list who warrant a little extra effort — and perhaps a slightly expanded budget — I offer a reliably foolproof formula: one handmade element, paired with one small store-bought companion.
From Salon • Dec. 23, 2025
A government-funded, industry-run trial looked at the main methods of age assurance and earlier this year reported all were technically possible – but none were foolproof and all carried risks.
From BBC • Dec. 6, 2025
“Those can be defeated but that can take a lot of time,” Sutter said.”It’s not foolproof but at least it’s a strong deterrent.”
From Los Angeles Times • Nov. 26, 2025
I did not, so I arranged to road-test the Breville Oracle Jet—a foolproof Cadillac for cappuccino lovers, I was told.
From The Wall Street Journal • Nov. 7, 2025
It’s a clever hiding place, but not foolproof.
From "Code Name Verity" by Elizabeth Wein
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
