It's an onomatopeia for a drum technique normally accompanying the conclusion of a cheesy joke or a comedy pratfall (where someone is made to look like an idiot by their own devising - such as falling on a banana skin they earlier discarded). It consists of two fast rimshots and a splash cymbal - producing the sound "badum tish".
#1: What does bees do if they don't want to drive?
#2: Dunno
#1: Wait at the buzz stop! Haha!
#2: Badum tish!
Also known as the JCB, the Jewish Car Baum is created when you combine a shot of cognac with a healthy amount of Manischewitz wine as a chaser. Please don't get this confused with an Irish Car Bomb, whose name is, indeed, derived from the JCB. Note that since it is a "Baum" and not a "bomb," the brave soul drinking this mess does not necessarily have to drop the shot into thier glass of Manischewitz. For the cognac, the creators recommend Courvoisier, because it makes you feel like a pimp.
Orheez: What drink has the highest reward of getting you hammered but also the greatest risk of causing you to vomit?