Is there another way to say 'secret handshake'?

This is called a dap greeting:

At its most basic, a dap greeting is simply a ritualized handshake, but it usually includes a series of gestures, with the gestures being performed in a specific and choreographed order. Many people learn dap greetings very young, by watching and interacting with other people in their communities, and often such greetings are exchanged almost reflexively, much like businessmen shake hands when meeting each other. A dap greeting can include snapping, wiggling fingers, slapping hands, and other forms of contact, and it can last anywhere from a few seconds to 20 minutes.

^wiseGEEK