dap 2 
(dăp)
(dăp)n.
1. An elaborate gesture of greeting developed by African American soldiers during the Vietnam War, usually consisting of a handshake and other maneuvers such as hand slaps and a fist bump.
2. A fist bump.
tr.v. dapped, dap·ping, daps
To greet by means of a dap.
[African American Vernacular English, of unknown origin.]