Index: trunk/data/validator/deprecated.mapcss
===================================================================
--- trunk/data/validator/deprecated.mapcss	(revision 8383)
+++ trunk/data/validator/deprecated.mapcss	(revision 8428)
@@ -477,2 +477,11 @@
   suggestAlternative: "sport=ice_hockey";
 }
+
+/* see #11471 */
+*[sport=billard],
+*[sport=billards],
+*[sport=billiard] {
+  throwWarning: tr("{0} is deprecated", "{0.tag}");
+  suggestAlternative: "sport=billiards";
+  fixAdd: "sport=billiards";
+}