尝试以下代码。

add_filter( \'gettext\', \'excerpt_gettext\', 10, 2 );
function excerpt_gettext( $translation, $original ) {
 $post_type = get_post_type( $_GET[\'post\'] );
 if($post_type == \'your custom post type\') {
   $text = strpos($original, \'Excerpts are optional hand-crafted summaries of your content that can be used in your theme\');
   if ($text !== false) {
     return  \'My Custom Excerpt Discription\';
   }
 }
 return $translation;
}

NOTE: Change "your custom post type" with your actual post type name