The definition of foolproof is something that is designed or set up so it would be difficult or impossible to make a mistake or an error during use.(adjective)
When an appliance is designed with very-simple to use buttons that even a really dumb person can use, this is an example of a time when the appliance is designed to be foolproof.
See foolproof in Webster's New World College Dictionary
See foolproof in American Heritage Dictionary 4
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