Definitions of fluke:

• noun:   parasitic flatworms having external suckers for attaching to a host
• noun:   either of the two lobes of the tail of a cetacean
• noun:   flat blade-like projection on the arm of an anchor
• noun:   a barb on a harpoon or arrow
• noun:   a stroke of luck
• name:  A surname (very rare: popularity rank in the U.S.: #20252)