This expression describes someone who is very upset or agitated, but in America it might be taken to mean someone who is just plain fucking ugly as well.
He: "What's your problem this morning? You have a face like the devil's ass today."
An adjective describing something either extremely hot (no, not hot as in hot attractive, hot as in hot temperature) like it came from the fiery depths of hell, having an ungodly stinking stench, or both.