The term refers to the erratic movements a new website will experience after first being indexed. Generally sites will jump straight to a very high position, before dropping to a very low position before ultimately settling in somewhere steadily.

Other than that, not much is known about it.

This just means your site jumps up and down the SERPS at complete random, one day it will be page 1, then not in the top 500, then on page 3, then page 5 and so on.

Eventually it will settle at a stable position.

Usually this is triggered after link building etc, and if your doing things right it should return at a higher position than it was at the start of the dance.

Hope that helps