Have a lot of pages you want removed from the Google index and don't want to use the page removal tool for each URL? Google's John Mueller said you can try to 404 and noindex all the pages you want removed and then submit a temporary sitemap to Google. It might speed things up he said.
John wrote in a Google Webmaster Help thread, "One way to speed this up could be to submit a temporary sitemap file listing these URLs with the last modification date (eg, when you changed them to 404 or added a noindex), so that we know to recrawl & reprocess them." "This is something you'd just want to do for a limited time (maybe a few months), and then remove, so that you don't end up in the long run with a sitemap file that's not needed by your site," he added.
So you can give this a try if you want to remove a lot of pages as fast as possible - although, I am not sure how fast this would be. Might still take days/weeks or even months for all the URLs to be removed?
Forum discussion at Google Webmaster Help.
