add glossary entry: standalone

Author: Bob Grabar

source/reference/glossary.txt

@@ -851,3 +851,7 @@ Glossary
       :term:`query`, that can be iterated through to retrieve
       results. By default, cursors will timeout after 10 minutes of
       inactivity.
+
+   standalone
+      In MongoDB, a standalone is an instance of :program:`mongod` that
+      is running as a single server and not as part of a replica set.

source/tutorial/convert-standalone-to-replica-set.txt

@@ -23,7 +23,7 @@ administration </replication>`, see:
 Procedure
 ---------
 
-These procedures assume you have a standalone instance of MongoDB
+These procedures assume you have a :term:`standalone` instance of MongoDB
 installed. If you have not already installed MongoDB, see the
 :ref:`installation tutorials <tutorials-installation>`.