Any attempt to make it better (and there has to be many in order to deserve this definition) only makes things worse and therefore enhances the definition of being "Zynga'd".
All attempts to make the game playable to the standard of the previous game were unsuccessful and led to further "Zynga-ups" in the game. Further attempts to improve the game to make it unexploitable have proven to be unmitigated failures and the developers of the game prove themselves to be inept, incompetent and inadequate to the tasks put to them.
Tha game is an application made by a company called Zynga - hence the definition.
Quote: "I didn't say it was broken, to be broken would imply that it can be repaired, it's not, it's zynga'd."
The company responsible for Farmville, Mafia Wars, Words with Friends, and a couple dozen knockoffs of more successful games. They make casual games on Facebook and cell phones centered around minimal skill, arbitrary wait times, excessive monetization, a flood of automated referrals spamming everybody's wall with requests to be somebody's neighbor, and their admitted use of scams and spyware.
Despite their games only being about as much fun as your screensaver at work and taking less effort to make than the average "10,000 Games on 1 CD!" shovelware, they tapped into the Pavlovian center of grandmothers the world over to the tune of billions of dollars in revenue and a nearly 20 billion dollar initial stock offering in 2011. They have since gone on a truly disastrous meltdown, with mass layoffs, executives bailing, their stock plummeting, insider trading and fraud accusations, and Electronic Arts suing them over plagiarism. Time will tell if they get buried like they deserve.