An individual whose very presence lowers the tone in the room. Will complain about almost anything and will dress in plain, understated clothes. The human equivilent of Eeyore from Winnie the Pooh.
"Hi everybody. Hope you're feeling better today than I am. Still can't find my Prozac anywhere, I'm getting really worried now. Must the Sun rise every morning in the east? Why can't..." - ad infinitum.