Glossary: Add term "base backup"

Author: Jürgen Purtz <juergen@purtz.de>
Discussion: https://postgr.es/m/95f90a5d-7692-701d-2c0c-0c88eb5cea7d@purtz.de

doc/src/sgml/glossary.sgml

@@ -178,6 +178,19 @@
    </glossdef>
   </glossentry>
 
+  <glossentry id="glossary-basebackup">
+   <glossterm>Base Backup</glossterm>
+   <glossdef>
+    <para>
+     A binary copy of all
+     <glossterm linkend="glossary-db-cluster">database cluster</glossterm>
+     files. It is generated by the tool <xref linkend="app-pgbasebackup"/>.
+     In combination with WAL files it can be used as the starting point
+     for recovery, log shipping, or streaming replication.
+    </para>
+   </glossdef>
+  </glossentry>
+
   <glossentry id="glossary-bloat">
    <glossterm>Bloat</glossterm>
    <glossdef>