A deceptive phrase used as a euphemism for masturbating while still using an instant messaging site or program. More commonly practiced by males, this phrase gained popularity as earlier phrases like "be right back" or "going to the bathroom" became too obvious.
Ted: "Dude, I tried to message you on MSN but you were 'away'"
David: "Sorry about that, I was making pasta. Don't tell Elizabeth though."
When you are too much of an uncultured swine to have the decency to make real tomato sauce for your pasta, you use ketchup instead. If this is you, find the morality to buy some jarred nasty Prego pasta sauce or whatever and toss it on your (probably not al dente) pasta.
Brenda, the spaghetti is almost ready, can you grab the ketchup? Mmm I love me some ketchup pasta!