A shorthand way of saying "modal window": a panel that appears over and disables the main content, requiring user interaction with it.
A modal window creates a mode that disables the main window but keeps it visible, with the modal window as a child window in front of it. Users must interact with the modal window before they can return to the parent application. This avoids interrupting the workflow on the main window. Modal windows are sometimes called heavy windows or modal dialogs because they often display a dialog box.
User interfaces typically use modal windows to command user awareness and to display emergency states, though interaction designers argue they are ineffective for that use.
From Wikipedia, submitted July 2021
