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A married person becomes sexually interested in someone else and decides to cheat on their spouse with them.

Comes from Arnold Swarchenegger cheating on Maria Shriver.
1) OMG, did you see that woman! I'm so Going Arnold! Don't tell Beth!

2) I know, I should not have cheated on Ginger, but Elizabeth was too hot not to. I lost my mind and decided to Go Arnold.
by Frank Darlucci May 19, 2011