Short for Diarrhea. It starts with a D, ends in the bathroom, and is never heard in polite conversation.
Sorry Professor, but I've been stricken with Silent D. Unless you can move that engine into the bathroom, I don't think I can run those tests you wanted today.
When you need to pee but you see something so arousing that you get hard and forget about using the toilet before beating your meat. The sensation you get during post nut clarity ends up being unbelievably painful, as if a fire was dwelling in your penis. It takes a long time to disappear and only gets worse depending what you pleasured yourself to.
Josh: " Dude, last night I had to pee so hard, but I saw a hot lewd of Astolfo and totally forgot he's a dude and that i had to pee. I tryed falling asleep with a silent fire in my pants and strong depression."
Jerry: "Wtf? I just asked for a little money."