Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 21158)
+++ wp-includes/taxonomy.php	(working copy)
@@ -2233,9 +2233,11 @@
  * @subpackage Taxonomy
  * @since 2.3.0
  * @uses $wpdb
+ * @uses apply_filters() Will call the 'wp_unique_term_slug' filter and pass
+ *  the resulting unique slug, the term, and the original slug.
  *
  * @param string $slug The string that will be tried for a unique slug
- * @param object $term The term object that the $slug will belong too
+ * @param object $term The term object that the $slug will belong to
  * @return string Will return a true unique slug.
  */
 function wp_unique_term_slug($slug, $term) {
@@ -2244,6 +2246,8 @@
 	if ( ! term_exists( $slug ) )
 		return $slug;
 
+	$original_slug = $slug;
+
 	// If the taxonomy supports hierarchy and the term has a parent, make the slug unique
 	// by incorporating parent slugs.
 	if ( is_taxonomy_hierarchical($term->taxonomy) && !empty($term->parent) ) {
@@ -2278,7 +2282,7 @@
 		$slug = $alt_slug;
 	}
 
-	return $slug;
+	return apply_filters( 'wp_unique_term_slug', $slug, $term, $original_slug );
 }
 
 /**