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.
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
The spokeswoman added that the company’s age prediction algorithms show performance similar to the rest of the industry, but will never be completely foolproof.
From The Wall Street Journal • Mar. 16, 2026
The trick to turning one deli run into multiple dinners is simple and nearly foolproof: one creamy, one crunchy, one briny or fresh.
From Salon • Feb. 12, 2026
My morale automatically went down, until I hit upon a foolproof reason why subunits should be helically arranged.
From "Double Helix" by James D. Watson
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.
