pop-up
ˈpop-up1 
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
pop-up2
noun [countable]
a window, often containing an advertisement, that suddenly appears on a computer screen, especially when you are looking at a website
| I |
adjective1. 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 |
noun [countable]a window, often containing an advertisement, that suddenly appears on a computer screen, especially when you are looking at a website