What does fluke mean?
'Fluke' is most familiar as a noun meaning an unexpected success or result brought about by luck rather than skill — the ace drawn at random, the shot that banks in off three surfaces, the job offer that arrives from nowhere. In this everyday sense it is informal to neutral in tone, and calling an achievement a fluke often implies skepticism about the achiever's ability. The word has a surprisingly varied other life: in biology, flukes are parasitic flatworms, such as the liver fluke that infects sheep and cattle; in American angling, especially in the northeastern United States, 'fluke' refers to the summer flounder; and in engineering, a fluke is the barbed arm of an anchor. This cluster of meanings reflects a tangled etymology: the luck sense probably arose from an older word for a flatfish, while the parasite and fish senses share the same root idea of something flat. Few common words range so widely, from good fortune to liver parasites.
A piece of good luck; a success or result obtained by chance rather than skill or intention.
"It was a fluke that she happened to be standing there when the celebrity walked in."
Informal to neutral; often used to discount the significance of an achievement.
A parasitic flatworm of the class Trematoda, some species of which infect the livers of mammals.
"Liver fluke is a serious problem for sheep farmers in wet regions."
Technical/scientific usage.
The summer flounder, a flatfish caught along the Atlantic coast of North America; also called fluke in angling contexts.
"We spent the morning fishing for fluke off Montauk."
Regional to US East Coast angling.
The barbed arm of an anchor, or the gripping end of certain tools.
"One of the anchor's flukes bent when it snagged on the rocks."
Technical/nautical usage.
Standard pluralization applies across all noun senses.
"Both flukes of the anchor were buried firmly in the seabed."
The word for a stroke of blind luck likely began life as the name of a flatfish — and it also literally means a parasitic worm.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fluke
English 'fluke' appears to derive ultimately from Old English 'floc', meaning a flatfish, which connects it to Germanic relatives like the modern German 'Flunder' and English 'flounder'. The lucky-chance sense emerged in the nineteenth century, apparently developing from billiards slang, where a lucky accidental shot was likened to a fluke fish. The parasitic-worm sense arose separately but naturally, since flukes were classified among the flatfish-like flatworms on account of their flattened shape. The name of Captain William Fluke, sometimes cited in older accounts, plays no genuine role in the word's development.
How fluke is actually used
In casual speech, 'fluke' almost always refers to a lucky accident and is informal to neutral in register. It can carry a faintly dismissive tone when used to downplay someone's achievement ('that was just a fluke'). The zoological senses (parasite, flatfish) belong mainly to scientific, veterinary, and angling contexts. The anchor-barb sense is largely technical.
Easily confused with fluke
'Flukey' (or 'fluky') is an adjective describing something dependent on or characterized by luck, whereas 'fluke' is the noun naming the lucky event itself.