Fish-tail propeller

from The Collaborative International Dictionary of English v.0.48

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]