I found this: note it is not my post! that icon means that you are using Download Booster is on. What this does is it will use Wi-Fi and your cellular data to download files more quickly. If you go to Settings>Connections>More you should be able to toggle it on or off. Let me know if that helps. My two cents: It has something to do with downloading large files over wifi and your cellular connection quickly. Are you doing such?