pop-up • adj. (of a book or greeting card) containing folded cut-out pictures that rise up to form a three-dimensional scene or figure when the page is turned. ∎ (of an electric toaster) operating so as to push up a piece of toast quickly when it is ready. ∎ Comput. (of a menu or other utility) able to be superimposed on the screen being worked on and suppressed rapidly.• n. 1. a pop-up picture in a book. ∎ a book containing such pictures.2. Baseball see pop1 (sense 3).3. Comput. a pop-up menu or other utility.