fishtail \fishtail\ v. i. to have the rear end skid from side to side, out of control: -- said of automobiles or other vehicles. [PJC] {Fish-tail burner}, a gas burner that gives a spreading flame shaped somewhat like the tail of a fish. {Fish-tail propeller} (Steamship), a propeller with a single blade that oscillates like the tail of a fish when swimming. [1913 Webster]