.TP 4
.BR \-\-exclude=(true|false|flag)
-Specify whether to omit messages matching search.tag_exclude from the
-search results (the default) or not. The extra option
+A message is called "excluded" if it matches at least one tag in
+search.tag_exclude that does not appear explicitly in the search terms.
+This option specifies whether to omit excluded messages in the search
+process.
+
+The default value,
+.BR true ,
+prevents excluded messages from matching the search terms.
+
+.B false
+allows excluded messages to match search terms and appear in displayed
+results. Excluded messages are still marked in the relevant outputs.
+
.B flag
only has an effect when
-.B --output=summary
-In this case all matching threads are returned but the "match count"
-is the number of matching non-excluded messages in the thread.
+.BR --output=summary .
+The output is almost identical to
+.BR false ,
+but the "match count" is the number of matching non-excluded messages in the
+thread, rather than the number of matching messages.
.RE
.SH EXIT STATUS