A marriage that is performed on impulse by one or both of the married couple. The couple may barely know each other or have just met and have decided to get married on the whim. A marriage based upon the satisfaction of the moment, just like Sigmund Freud's theory of the id.
Also, an impulsive marriage that is based on what are considered to be odd reasons to get married (i.e. spur of the moment, love at first sight, etc)
"She was dating this guy for one week, and now this wedding is going to be Id's marriage!"