This is a bit different than my typical word posts, because I don't recall hearing it before. I probably have somewhere, but when I came across the mention of the word in Peter Carey's novel Parrot and Olivier in America today, I had no idea what he was talking about. Luckily, Carey is too savvy to assume anything about his readership's vocabulary, so he has the boy Parrot be equally perplexed and then reveals it's use to all of us before too long. As the boy says:
You do not know what a burin is, and nor did I, mistaking it for a shiv, a murdering steel shaft with a hemispherical handle.
A burin, it turns out, is an engraver's tool. Can you visualize it? Good for you. I can't. I'm going to need a visual...
In the book, Parrot learns to carve into a block of exceedingly hard wood, but most of the stuff I've come across here has to do with carving into metal--or stone. Here's a very informative video I came across:
After watching this video, you may understand why Wikpedia has a picture of the Dutch artist Hendrik Goltzius's hand which was said to be particularly suitable for using a burin:
Sounds about right.