Delete the pages from your site (so that the server returns 404 for the requests of this URL) or prohibit its indexing using robots.txt file.
Then use the “Delete URL” form. Now, next time the robot accesses your site, all the pages that have been removed or prohibited for indexing will disappear from the search results.
Prohibition of indexing does not guarantee that the site will disappear from the search results, because it may be searched through links published on external sites.
As soon as the robot discovers that the page was deleted, it will remove it from indexing. To speed up the process, use the “Delete URL” form.