diff --git a/docs/glossary.rst b/docs/glossary.rst
index f4912f5..a062319 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -15,6 +15,10 @@
    AArch64
       64-bit execution state of the ARMv8 ISA
 
+   AMU
+      Activity Monitor Unit, a hardware monitoring unit introduced by FEAT_AMUv1
+      that exposes CPU core runtime metrics as a set of counter registers.
+
    API
       Application Programming Interface