Perfected by but not restricted to Japanese people. The ability to fall asleep when ever they want/need to anywhere. eg Sitting on the bus or standing on the train.
Dude 1: "Dude, it looks like that Asian guy is alseep!"
Dude 2: "He is, he's having a Jap nap"
Dude 2: "Ahh soo!"
Asian guy: "zzzzzzzzzzzzzzz"