fluke fluke /ˈfluːk/

noun

1. Parasitic flatworms having external suckers for attaching to a host  ( fluke , trematode , trematode worm )
   parasitic flatworms having external suckers for attaching to a host
   
   
2. Either of the two lobes of the tail of a cetacean  ( fluke )
   either of the two lobes of the tail of a cetacean
   
3. Flat bladelike projection on the arm of an anchor  ( flue , fluke )
   flat bladelike projection on the arm of an anchor
   
4. A barb on a harpoon or arrow  ( fluke )
   a barb on a harpoon or arrow
   
5. A stroke of luck  ( fluke , good fortune , good luck )
   a stroke of luck