/pop"up'/ , adj.
1. (of books, usually children's books) having pieces of artwork fastened to the pages so that when the page is opened, a three-dimensional cutout or object is formed and, sometimes, movement of a picture element, such as a door opening, can be activated by pulling a tab.
2. of or being a device that ejects or raises a finished or used item from the top: a pop-up toaster.
3. of or pertaining to a device, mechanism, or object that rises or pivots from a concealed or recessed position to its operating position: a camera with a pop-up electronic flash; a car with pop-up headlights.
4. popping up, as from an appliance or object: pop-up waffles heated in the toaster; a pop-up gauge for indicating when the turkey is done.
5. a pop-up book.
6. something, as a partially cut out or spring-mounted illustration in a children's book, that unfolds or springs up when opened or otherwise activated; pop-out: a Christmas card with a pop-up of Santa Claus.
7. Baseball. See pop fly .
Also, popup .
[ 1860-65 for def. 7; n., adj. use of v. phrase pop up ]