It's the "doctor" term for the Lazy Disorder. Yeah, it exists, what do you think? Ahaha!
Person 1: Hey did you do your home works already?
Person 2: No.
Person 1: Why?
Person 2: Because I have L.D.
Person 1: What's that?
Person 2: Layzous Disorderous. It's for people who are so lazy it becomes a disorder.