Slang for a tablet of No-Doz Plus. Used most often by comp sci majors, hackers, and cyberpunks due to it sounding more "edgy" and interesting. ND tab is, of course, the alternate slang for regular No-Doz.
Guy 1: "Hey man, you tired?"
Guy 2: "Nah, I'm still zapped from the two tabs of NDP and the three cups of coffee I had before I left the house."
Guy 1: "Man, we're going to be up all night writing this program."
Guy 2: "I'm already tired. Pass me an NDP tab."