DoucheBlock is an easy to use Twitter extension that allows you to block users based on their Twitter profile. Simply download and install the extension from the Google Play Store, then choose your keywords for blocking and you're good to go. The app scans Twitter profiles for people who use the specified keywords, and if a match is found, the user will be blocked. It doesn't show a notification or banner on the screen, but instead, it simply starts watching for the user and updates in the background. There are plenty of reasons why you may want to block someone on Twitter.