Add more entries to the glossary.

Written by Jeff Wheeler for GHOP.
diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst
index a4b271f..11af432 100644
--- a/Doc/library/contextlib.rst
+++ b/Doc/library/contextlib.rst
@@ -17,9 +17,9 @@
 
 .. function:: contextmanager(func)
 
-   This function is a decorator that can be used to define a factory function for
-   :keyword:`with` statement context managers, without needing to create a class or
-   separate :meth:`__enter__` and :meth:`__exit__` methods.
+   This function is a :term:`decorator` that can be used to define a factory
+   function for :keyword:`with` statement context managers, without needing to
+   create a class or separate :meth:`__enter__` and :meth:`__exit__` methods.
 
    A simple example (this is not recommended as a real way of generating HTML!)::