This is when many identical glasses are lined up, all but one at the end filled with Red Bull, shot glasses placed on the rims to straddle each gap between glasses and filled with Jägermeister, then the shot glass at the end is tipped over. If done correctly, all the shot glasses will fall in a domino rally and create many Jäger bombs in rapid succession.
Fifteen people in a row at the bar all ordered Jäger bombs, so the bartender set up a Jäger train to serve them all.
A rule that Texas Hold'em players use stating that on the flop, a player's chances of making a hand are approximately 4% times the number of cards in the deck (outs) that would make the hand.
I have J-10 and the flop is Q-9-5, giving me an open-ended straight draw. With four eights and four kings in the deck that can make my hand, the Rule of Four states that my chances of getting the straight are 32%.