add intrinsics to glossary

src/appendix/glossary.md

@@ -36,6 +36,7 @@ ICH <div id="ich"/>                      |  Short for incremental compilation ha
 infcx <div id="infcx"/>                  |  The inference context (see `librustc_middle/infer`)
 inference variable <div id="inf-var"/>   |  When doing type or region inference, an "inference variable" is a kind of special type/region that represents what you are trying to infer. Think of X in algebra. For example, if we are trying to infer the type of a variable in a program, we create an inference variable to represent that unknown type.
 intern <div id="intern"/>                |  Interning refers to storing certain frequently-used constant data, such as strings, and then referring to the data by an identifier (e.g. a `Symbol`) rather than the data itself, to reduce memory usage and number of allocations. See [this chapter](../memory.md) for more info.
+intrinsic <div id="intrinsic"/>          |  Intrinsics are special functions that are implemented in the compiler itself but exposed (often unstably) to users. They do magical and dangerous things. (See [`std::intrinsics`](https://doc.rust-lang.org/std/intrinsics/index.html))
 IR <div id="ir"/>                        |  Short for Intermediate Representation, a general term in compilers. During compilation, the code is transformed from raw source (ASCII text) to various IRs. In Rust, these are primarily HIR, MIR, and LLVM IR. Each IR is well-suited for some set of computations. For example, MIR is well-suited for the borrow checker, and LLVM IR is well-suited for codegen because LLVM accepts it.
 IRLO <div id="irlo"/>                    |  `IRLO` or `irlo` is sometimes used as an abbreviation for [internals.rust-lang.org](https://internals.rust-lang.org).
 item <div id="item"/>                    |  A kind of "definition" in the language, such as a static, const, use statement, module, struct, etc. Concretely, this corresponds to the `Item` type.