To remove Boomerang completely from your Chrome Web browser, open Chrome and click the Chrome Menu button--which is shaped like a wrench--on the toolbar. Point to "Tools" and click "Extensions." The list of currently installed extensions opens. Click the "Remove from Chrome" button, which looks like a trash bin, next to Boomerang for Gmail. Click "Remove" when a Confirm Removal prompt window appears. Once you have uninstalled the plugin, you can revoke the app's rights to your Gmail account.