The Collaborative International Dictionary of English v.0.48:
Flounce \Flounce\, v. i. [imp. & p. p. Flounced (flounst); p.
pr. & vb. n. Flouncing.] [Cf. OSw. flunsa to immerge.]
To throw the limbs and body one way and the other; to spring,
turn, or twist with sudden effort or violence; to struggle,
as a horse in mire; to flounder; to throw one's self with a
jerk or spasm, often as in displeasure.
To flutter and flounce will do nothing but batter and
bruise us. --Barrow.
With his broad fins and forky tail he laves
The rising sirge, and flounces in the waves. --Addison.