An emoticon used to express (mostly comedic or exaggerated) agony, distress, anger, or suffering.
Usually used in chats.
B-"Um. I'm so sorry ): I can't go."
A- "D8 WHYYYY!"
Second of all, it can be a smilely with D as the mouth and 8 as the eyes. Not many people know what it means, but I believe it may be an extreme case of D:
Person 1: *Cough cough* I'm dying... x_x
Person 2: No!! D8 Don't die!!
usually a designated time to get online to talk to this specific person
"Oh yeah? Where at?"
"Me and HotChick69 are meeting in a private chat-room at 8:30."
"Nice! Maybe you'll get some n00dz!"