Definition of "pop up" in English

Verb

1. To come up with a "pop" sound.

   • The toast is in the toaster - when it pops up it will be ready.

2. To appear without warning.

   • I can't remember where I left my keys, but they normally pop up somewhere.

3. (Of an alert, advertisement, etc.) To suddenly appear onscreen.

4. To display as an alert, advertisement, etc. that suddenly appears on screen.

   • My computer just popped up a warning about Internet security.