Difficult

Yes, expensive headache!

Dramatic.

If you are listing this home and looking for words to describe this area, I would say "soaring, dramatic curved bay window area, perfect for a piano or intimate seating area,". If you are a buyer I would hope you could put a lacquered piano or a custom curved sectional arrangement in this area for a lovely seating spot. Lots of options. Since it appears there is a patio roof outside you don't even need window treatments if you don't want them. You could do 20' drapery panels on the outside edges just to soften the area if that is your design sense.

I looked again at these pictures and it appears these photos are all of different homes, so I am a bit confused about your question. Are you just curious about what they are called? Are you considering purchasing a home with these; building a new home? More info would be helpful.

Mcmansionhell calls it a pringles can