a horseshoe up (one's) ass

vulgar slang What one is said to have when experiencing extremely good luck, fortune, or favor. A horseshoe is thought to be a symbol of good luck. Wow, that's the third hand of poker I've won in a row—it's like I have a horseshoe up my ass today! You really won an all-expenses-paid trip to the Bahamas? You lucky fool—you've sure got a horseshoe up your ass. Have I ever won any money from playing the lottery? No—I'm really starting to think you need a horseshoe up your ass to pull that off.