Foolproof
WordNet
adjective
(1) Not liable to failure
"A foolproof identification system"
"The unfailing sign of an amateur"
"An unfailing test"
verb
(2) Proof against human misuse or error
"Foolproof this appliance"
WiktionaryText
Adjective
- For a device: protected, or designed to be proof against misuse or error; fail-safe.
- For an idea or plan: infallible, or bulletproof.