I. ˈpop-up 1 BrE AmE adjective
1 . pop-up book/card etc a book, card etc with a picture that stands up when you open the pages
2 . pop-up menu/window a ↑ menu or ↑ window that can appear suddenly on a computer screen while you are using it
II. pop-up 2 BrE AmE noun [countable]
a ↑ window , often containing an advertisement, that suddenly appears on a computer screen, especially when you are looking at a website