What is "throbber"

n. (context graphical user interface English) A widget consisting of a static image that animates during execution of a task.

A throbber is an animated graphical control element used to show that a computer program is performing an action in the background (such as downloading content, conducting intensive calculations or communicating with an external device). In contrast to a progress bar, a throbber does not convey how much of the action has been completed.