Add table listing verbosity levels in documentation.

docs/source/usersguide/input.rst

@@ -839,13 +839,25 @@ problem. It has the following attributes/sub-elements:
 
     *Default*: None
 
+.. _verbosity:
+
 ``<verbosity>`` Element
 -----------------------
 
 The ``<verbosity>`` element tells the code how much information to display to
 the standard output. A higher verbosity corresponds to more information being
 displayed. The text of this element should be an integer between between 1
-and 10.
+and 10. The verbosity levels are defined as follows:
+
+  :1: don't display any output
+  :2: only show OpenMC logo
+  :3: all of the above + headers
+  :4: all of the above + results
+  :5: all of the above + file I/O
+  :6: all of the above + timing statistics and initialization messages
+  :7: all of the above + :math:`k` by generation
+  :9: all of the above + indicate when each particle starts
+  :10: all of the above + event information
 
   *Default*: 7
 

openmc/settings.py

@@ -142,7 +142,8 @@ class Settings(object):
         Mesh to be used for redistributing source sites via the uniform fision
         site (UFS) method.
     verbosity : int
-        Verbosity during simulation between 1 and 10
+        Verbosity during simulation between 1 and 10. Verbosity levels are
+        described in :ref:`verbosity`.
     volume_calculations : VolumeCalculation or iterable of VolumeCalculation
         Stochastic volume calculation specifications