A more thorough explanation:

Definition: Full proof means that something is completely certain or guaranteed to work. It is a variation of the term "foolproof."

Example: The new security system is full proof, ensuring that no unauthorized individuals can enter the building.

Explanation: The example illustrates that the security system is completely certain to work and is guaranteed to prevent unauthorized individuals from entering the building. The term "full proof" emphasizes the level of certainty and reliability of the security system.