Add "item" to glossary

Author: varkor

src/appendix/glossary.md

@@ -34,6 +34,7 @@ inference variable      |  when doing type or region inference, an "inference va
 infcx                   |  the inference context (see `librustc/infer`)
 IR                      |  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                    |  `IRLO` or `irlo` is sometimes used as an abbreviation for [internals.rust-lang.org](https://internals.rust-lang.org).
+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.
 lang item               |  items that represent concepts intrinsic to the language itself, such as special built-in traits like `Sync` and `Send`; or traits representing operations such as `Add`; or functions that are called by the compiler. ([see more](https://doc.rust-lang.org/1.9.0/book/lang-items.html))
 local crate             |  the crate currently being compiled.
 LTO                     |  Link-Time Optimizations. A set of optimizations offered by LLVM that occur just before the final binary is linked. These include optimizations like removing functions that are never used in the final program, for example. _ThinLTO_ is a variant of LTO that aims to be a bit more scalable and efficient, but possibly sacrifices some optimizations. You may also read issues in the Rust repo about "FatLTO", which is the loving nickname given to non-Thin LTO. LLVM documentation: [here][lto] and [here][thinlto]