Comput. a window, containing a message or menu, that appears superimposed over the window in use, often, specif., one containing an advertisement from the Web
adjective
of or designating a book designed so that cut-out portions of an illustration lift when the book is opened to its page, producing a three-dimensional effect
See pop-up in American Heritage Dictionary 4
(pŏpˈŭpˌ)
adjective
Emerging quickly from a recessed or concealed position when activated: pop-up gun emplacements.
Rising to form a three-dimensional structure when a page is opened: pop-up illustrations in a children's book.