An emoticon showing a male masterbating.
o is the head
G is the guy's arms with the inner hook of the letter representing a well-gripped and erect penis.
< is the legs of the male.
<deltaco> where's tac0r been?
<Tacolas> probably oG<
<deltaco> thought tac0r was a she, shouldn't it be o8>< ?
<Tacolas> with a robot you can never tell