What is "pops up"

Usage examples of "pops up".

A boy with a machete cuts the one remaining line, which pops up and lashes him across the face.

A box pops up giving him several KEY LENGTH options: 768 bits, 1024, 1536, 2048, 3072, or Custom.

Now they were smiling and nodding yes to Heaven, with the kind of expressions people in the theater get on their faces when a famous director pops up, even one who makes documentary films and so can't cast them in his next production.

Zack's face pops up in the window to the right of the front door, and he is crying.

If it pops up once every ten thousand or hundred thousand years, how can we defend that it is, in any sense, a separate organic concern, a purely pathogenic particle?

Forcing himself to go on, he cues up the news and one of the perfect hair guys, Karl can't tell any of them apart, pops up sitting in the slow lane, as if perched on the tailgate of the transport ahead.