It's an underperformance. The art itself has been less than satisfactory for many, myself very much included. However, it's not a flop.
And don't with these "for Gaga's standards" posts - either it is or it isn't. You don't get to redefine the word "flop" to be relative to one pop star, that's literally what the word "underperformance" is for in this field.
Why are people so obsessed about whether or not ARTPOP is labeled a "flop" or "smash"? It doesn't matter, you are just a speck in the universe and so is the album.
It's underperforming by her past success, but it's not at all a flop. She should be happy. The video releases are sloppy, but if this is the music she really wants to make like she said, than she should be happy with it's success. 2 platinum singles and a #1 albums pretty good in my book haha