A popup is a window item displayed in front of other content, at a certain event in a software.
A popup is a window item displayed in front of other content, at a certain event in a software. Usually the content behind the popup can't be accessed until the popup message action has been made, even if the only choice is OK. A popup menu (also named context menu) is visible on right clicking a control.

Questions with the popup tag regards development and use of popup menu items.