Issue #10357: Clarify what it means to be a mapping.
diff --git a/Doc/glossary.rst b/Doc/glossary.rst
index 9ec61de..ec8af62 100644
--- a/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@ -428,9 +428,11 @@
:class:`importlib.abc.Loader` for an :term:`abstract base class`.
mapping
- A container object (such as :class:`dict`) which supports arbitrary key
- lookups using the special method :meth:`__getitem__`. Mappings also
- support :meth:`__len__`, :meth:`__iter__`, and :meth:`__contains__`.
+ A container object that supports arbitrary key lookups and implements the
+ methods specified in the :class:`Mapping` or :class:`MutableMapping`
+ :ref:`abstract base classes <abstract-base-classes>`. Examples include
+ :class:`dict`, :class:`collections.defaultdict`,
+ :class:`collections.OrderedDict` and :class:`collections.Counter`.
metaclass
The class of a class. Class definitions create a class name, a class