Something said in response to someone getting
owned. Can also be applied to other objects, as in "C me," "C him," "C them," etc.
Your
buddy: It took me 20 minutes to get to your house because of this old lady driving in front of me.
You: Heh, CU!
Your
buddy: Yeah, but since it took so
long, the ice cream I brought melted.
You: Ooh, C us.