This is the 4074th most frequent Japanese word.
フラッ
"フラッ" refers to something happening momentarily or casually, like a fleeting action or unexpectedly stopping by.
"フラッと" in this context implies a casual, unplanned or spontaneous action.
彼はフラッと店に立ち寄った。
He stopped by the shop casually.
Here, "フラッと" describes a loose, casual appearance or feeling, applied to the hairstyle.
フラッとした髪型が彼女に似合っている。
The soft, loose hairstyle suits her.
"フラッと" denotes a sudden, unsteady motion or action, like collapsing.