Used another way, «proof» can mean keeping something unwanted from getting in. (educationworld.com)
Even if you have to stop in a destination for a few hours, please make sure that the destination is covered under that policy, just in case something unwanted happens. (policybazaar.com)
Still, some nurse sharks can grow up to 14 feet long and even the smaller ones could still get a little aggressive and cause you some unwanted issues. (uponarriving.com)