a normal dap is a form of greeting( handshake) where two people bump fists. not up and down but sraight foreward like theyre punching each others fist. a double dap is with both hands, but it is saved for only the illest of occasions.
1:dude you banged that chick last night?
2: motions for dap
1:no dude, double dap
1/2: both execute the double dap