From the song by Nick Cave & the Bad Seeds, used to describe the depressed feeling you get about the modern world in general. An abattoir is a slaughterhouse, so the term, in a more in depth way, means you feel the world is lining itself up for slaughter, much like cows do at a slaughterhouse.
Man 1: Hey, are you all right? You've seemed kinda depressed lately.
Man 2: Oh, it's okay, I've just got a case of abattoir blues.