Zip It is a OneLouder exclusive feature that lets you hide annoying tweets or tweeters without unfollowing! Here's how it works in the Android version:
You see a tweet that you want to "zip"
Tap the tweet you want to zip then select "Zip It" from the tweet options dialog.
The Zip It screen will display. Here you can choose you if you want to zip the tweeter, or some content from their tweet (you will see checkboxes for each zippable item).
From then on, tweets from that tweeter or with the applicable content will be zipped. A zipper graphic will appear in place of the zipped content in the timeline.
You can easily unzip the content by tapping the zipper icon, checking the checkbox for the item you wish to unzip and then tapping "Unzip."