So, it's really a kind of insult to the russians coming back from… daaah! what else? the Cold War days, when they were the Evil Ones.
(At least that's what I… grasped, if you will, the first time I've heard it… but not being english my mother-tongue, I'm probrably wrong)
… (…)…(…)…(…)…DAAAAHH!! (you all know the entonation)
Jason: DAH ! Are you shittin' me ?!
Jenna:. . . And then she like totally went in and-
Jason; DAAH !! YOUR SO DAMN ANNOYING shut up !!
Situation 2: This word could be used to retaliate from a verbal attack in a friendly and joking way.
This was first used as an inside joke when one friends status was in German and the other friend commented "Dah" because he didn't understand the status as a joke. Then, for every other comment he didn't know how to respond to he said "Dah"
A: "Uhhhhh Dah?"
Q: "Wow, you are horrible at football."