fishtail

A type of hair braid or a dress/skirt style that flares out at the bottom.

"She wore her hair in a fishtail braid."

To swing the rear of a vehicle or aircraft from side to side, often losing control.

"The car fishtailed on the icy road."

A side-to-side swinging motion of a vehicle's rear, often indicating loss of control.

"The driver corrected the sudden fishtail."