(verb)
to move or go somewhere, especially to leave a place, in a way that is exaggerated and determined, usually to show one's anger or impatience;
e.g. We watched her flounce out of the room when she got tired of waiting.
(noun)
an exaggerated physical gesture, such as a toss of the head, that is intended to show one's impatience or or annoyance;
e.g. He gave a flounce of his head as he criticized their work.
(noun)
a frill or a ruffle, a strip of fabric that is gathered and sewn together and then attached to the lower hem of a garment such as a skirt or a dress as decoration;
e.g. The dress had a wide flounce at the bottom.