Telling someone to literally fall into a pot hole while walking. To wish death on someone in the most disgusting and vile manner, to die in the sewer system after falling into a pot hole, especially the sewer system of a large city ie. New York City, where the rats are bigger than cats.
This is mainly used to express the feeling of mortification after a particularlyhumiliating social experience, leaving you wanting to "crawl in a hole and die" rather than face the people it happened in front of.
Susan: Did you really skip wearing underwear today?
Angela: Yes! And everyone at school saw when I fell down! I just wanna crawl in a hole and die, now