To rubberneck means:
To turn one's head to stare at something in a foolish manner.
Example: "a passerby rubbernecking at the accident scene"
What's the translation of "rubberneck" in French?
Google translate and DeepL didn't help.
There is a translation in a Robert-Collins dictionary; however, I don't like it very much; for one thing, there is no twisting of the neck implied.
rubberneck faire le badaud
A precise translation requires quite some phrasing. The following is an option of multi word translation.
A passerby rubbernecking at the accident scene.