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.
It still isn’t foolproof, and it is wise to use an actual flesh-and-blood human to fact-check anything you must get right.
From The Wall Street Journal • May 19, 2026
While some might think signing Bauer might be a risky move for an MLB organization, Bauer feels his plan is foolproof in that regard.
From Los Angeles Times • May 8, 2026
Kelly is no foolproof indicator of where the right is headed; she bet against Trump, after all.
From Slate • May 6, 2026
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
It was hardly foolproof; indeed, it was almost certain to fail more often than it succeeded.
From "The Big Short" by Michael Lewis
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.
