"Nahverteidigungswaffe" is a German word that means "close-range defense weapon". It's something that you can use if someone tries to hurt you when they're very close to you - like if they're standing right next to you.
Nahverteidigungswaffen can be different things, but they're usually small and easy to carry. Examples include pepper spray, a pocket knife or other small blade, and a stun gun. These tools can help you protect yourself if someone tries to attack you while you're out and about.
It's important to remember that while nahverteidigungswaffen can be useful, they're not a guaranteed protection against harm. If you ever feel like you're in danger, it's important to try and get away and seek help from a trusted adult.