Okay kiddo, have you ever seen a buck? They're those animals with big antlers on their heads. Sometimes, those antlers can get damaged and form a hole in them. That hole is called a "hole in the horn buck."
Now, imagine you have a cup made of plastic. If you accidentally step on it, it might crack or get a hole. That's what happens to a buck's antlers if they get hit or bumped really hard. The antler grows around the damaged part, forming a new layer of antler material over it.
The buck with the hole in the horn might look a little funny or different from other bucks because of the horn's odd shape. But don't worry, it doesn't hurt the buck or affect its ability to live and survive in the wild. In fact, it might even give the buck an advantage in some situations, like being able to reach food that other bucks can't.
So, that's what a hole in the horn buck is. It's just a buck with a tiny hole in its antlers that doesn't cause any problems for the animal.