How would you define a flop?

[Bokal]

We often see on this site threads about how a game is a flop, then goes an endless thread of "yes it is. no it isn't".

So when, for you, is a game a flop?

 

When it doesn't reach the 1M mark?

When it doesn't sell more than 1/20th of the system owner base?

When the devs don't get their money back?

When it doesn't reach expectations?

When it does sell less than the average of its genre?

 

I think you get the idea behind my question now...