What word means you should disconnect it completely from its electrical source then you have to make sure that the electricity cannot be reconnected by you or anyone else until it is safe again?

The Word you're looking for is "lockout." Lockout refers to a safety procedure in which a device is completely disconnected from its electrical source and secured to prevent re-energization until it is deemed safe for operation. This ensures that no one can inadvertently restore power while maintenance or repairs are being conducted.