diff --git a/Glossary.md b/Glossary.md
index fe28f63..5eb0516 100644
--- a/Glossary.md
+++ b/Glossary.md
@@ -22,7 +22,7 @@ Intermediate representation. Typically represented as instructions that referenc
 
  * ZIR
  * AIR
- * MIR (proposed)
+ * MIR (stage2 only)
 
 There is also LLVM IR.
 
@@ -45,6 +45,10 @@ Does type checking, comptime control flow, and safety-check generation. This is
 
 See `src/Sema.zig`.
 
+### MIR
+
+Machine Intermediate Representation, lowered to from AIR. Each instruction set architecture will have its own MIR dialect as it is designed to closely match available instructions. Designed for stage2+, since LLVM and C backends don't need MIR. Partially implemented. See [the design issue](https://github.com/ziglang/zig/issues/9514).
+
 ### ZIR
 
 Zig Intermediate Representation. `src/Astgen.zig` converts AST nodes to these