This is the 2963rd most frequent Japanese word.
スタイリッシュ
Stylish.
Here, "スタイリッシュ" is used as a descriptive adjective to describe the dress's fashionable appearance.
彼女のドレスはとてもスタイリッシュですね。
Her dress is very stylish.
In this case, "スタイリッシュ" modifies the word "雰囲気" (atmosphere), commenting on the sophisticated and trendy ambiance.
そのレストランはスタイリッシュな雰囲気で人気があります。
The restaurant is popular for its stylish atmosphere.
Here, "スタイリッシュ" is applied to describe the solution as being elegantly conceived or cleverly designed.