Discourse dialogue is also compressed and moves rapidly, like a ball in a ping-pong match. The verbal exchanges move back and forth between characters, shifting power from one side to the other, until somebody scores the point.
Screenplay dialogue needs to be full of conflict as well, lots of it. Never make it too easy for any character. Especially in a heated argument when emotions are running high, words often become the weapons of choice, and the wounds they inflict can be much deeper than any sharp blade.
Rarely, however, do characters say exactly what they mean: dialogue exchanges are all about SUBTEXT. Done properly, a good dialogue interaction will not only move the story forward but also flesh out your characters at the same time.