Screenwriting : Terminology by Andrew Gardner

It often means that your dialogue is too revealing, too obvious. For example: A character slams his fist on the table, and then says: I'm so pissed at you! - Well, the reader/audience figured that by the character's actions. Too much on the nose dialogue and no subtext is really boring. Here's some info on it: http://bit.ly/1QZP9gU

Yup, "on the nose" means the dialogue is "telling" what the character is thinking or feeling; that they are stating their exact reasons for their behavior or what is taking place; that they are "all knowing" and overly self-aware—in other words, boring. Subtext or hidden meaning brings dialogue and action to life. People rarely say/do exactly what they mean or what they are thinking. For a quick example, I'll use the great line from JERRY MAGUIRE, "You had me at 'hello.'" Subtext meaning: Yes, I'll take you back. I love you too. :) I hope that helps, Andrew!