Dirty Gamble
A "Dirty Gamble" is an instance where a betting or gambling situation is created with set rules. And after the game is created and the bet and/or wager is made, the rules are changed.
Hey I won the 4th quarter on the super bowl squares, where is my money. I'm sorry I told everyone that I could find at work the day before the super bowl that it's final score not 4th quarter. I was not at work that day. That was a dirty gamble.