diff --git a/docs/glossary.rst b/docs/glossary.rst
index a062319..aeeb133 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -92,6 +92,10 @@
    MPAM
       Memory Partitioning And Monitoring. An optional Armv8.4 extension.
 
+   MPMM
+     Maximum Power Mitigation Mechanism, an optional power management mechanism
+     supported by some Arm Armv9-A cores.
+
    MPIDR
       Multiprocessor Affinity Register