foolproof

[ fool-proof ]
/ ˈfulˌpruf /

adjective

involving no risk or harm, even when tampered with.
never-failing: a foolproof method.

Origin of foolproof

An Americanism dating back to 1900–05; fool1 + -proof
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for foolproof

British Dictionary definitions for foolproof

foolproof

/ (ˈfuːlˌpruːf) /

adjective

proof against failure; infalliblea foolproof idea
(esp of machines) proof against human misuse, error, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for foolproof

foolproof


adj.

also fool-proof, 1902, American English, "safe against the incompetence of a fool," from fool (n.) + proof.

Online Etymology Dictionary, © 2010 Douglas Harper