A greeting exchanged on the Jewish Sabbath (or any other day of the week).
One party to the greeting exclaims "Shabbat fistbump!" and pounds the other person's fist.
An energizing upgrade from the traditional Shabbat handshake.
Person 1: Shabbat shalom (peaceful Sabbath) my friend, how was your week? (extends hand)
Person 2: Shabbat fistbump, dude!!! (extends closed fist)
Person 1: (pounds it) That was so much more fulfilling than a regular handshake.