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
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Old Yeller
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
The Bad Beginning
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
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.
Not that it was foolproof, but it was just such a silly idea and I was a fan of David Wain and those guys anyway.
From Los Angeles Times • Jul. 6, 2026
But the Dutch blueprint isn't foolproof - youth unemployment is rising.
From BBC • Jun. 7, 2026
Kelly is no foolproof indicator of where the right is headed; she bet against Trump, after all.
From Slate • May 6, 2026
Within months, the scam had become so foolproof, the government said, that in April 2023, Hennen reassured a co-schemer by sending a text message.
From The Wall Street Journal • Jan. 15, 2026
Jerry, however, did not give a foolproof reason for preferring the keto forms.
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.
