Modal

Definitions

A UI overlay dialog that appears on top of the current view and blocks interaction with the content behind it until the user dismisses it or completes the required action, commonly used for confirmations, forms, and alerts.
In plain English: A pop-up box on a screen that forces you to deal with it before you can do anything else on the page.
Example: "The delete confirmation is a modal — you can't click anything else until you explicitly confirm or cancel."