When one person knows about something and the other person they are talking to thinks they dont know.
If a person is trying to get off the phone the other person will respond to that person by showing them they have a loaded phone book and can easily call and talk to someone else.
If Chantel is talking to Ron and Ron wants to get off the phone and makes an excuse to try and get off the phone, Chantel will respond to Ron catching his lie, "Oh, you so you're clothes are ready to be put in the dryer from the washing machine, huh? Alright player, uh huh, DEX KNOWS PLAYER, DEX KNOWS.
Definition 2 Example:
If Chantel is talking to Ron and Chantel starts to act like she's too cool for the conversation, Ron will show he has other options and respond with, "Alright Chantel, thats fine, I dont need to talk to you, I got my phone book, Dex knows, Chantel, Dex knows." This shows Chantel that Ron has options and he can do him.