A blivet, also known as a poiuyt, is an undecipherable figure, an optical illusion and an impossible object. It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.
 Paradoxical graphic figure
In its most common usage, the blivet is an indecipherable figure, illustrated above. It appeared on the March 1965 cover of Mad magazine, where it was dubbed the “poiuyt” (the last six letters on the top row of many Latin-script typewriter keyboards, right to left), and has appeared numerous times since then. An anonymously-contributed version described as a “hole location gauge” was printed in the June 1964 issue of Analog Science Fiction and Fact, with the comment that “this outrageous piece of draftsmanship evidently escaped from the Finagle & Diddle Engineering Works”
 Military usage
In traditional U.S. Army slang dating back to the Second World War, a blivet was defined as “ten pounds of manure in a five pound bag” (a proverbial description of anything egregiously ugly or unmanageable); it was applied to an unmanageable situation, a crucial but substandard or damaged tool, or a self-important person. In Cormac McCarthy‘s All the Pretty Horses, Rawlins defines a blivet as “10 pounds of shit in a 5 pound bag”. During the Vietnam War, a heavy rubber bladder in which aviation fuel or POL (petroleum, oil, and lubricants) was transported was known as a blivet, as was anything which, once unpacked, could not be replaced in its container. The usage of blivet for a fuel container is still current. A recent request for quotation (‘Solicitation number W91B4P-07-Q-0615 titled “Fuel Point Bill of Materials”‘) in Afghanistan includes a line item for “10 50,000 gal. blivets” .
In various United States Air Force communities (e.g. Strategic Air Command), blivet may have referred to what are euphemistically called “Special Weapons” whose presence are officially neither confirmed nor denied. Usage apparently derived from the original cavalry definition.
In some areas of the U.S., it refers to a juvenile prank, clearly connected with the original military usage: a sack full of excrement is ignited on the victim’s porch, while the pranksters ring the doorbell and run. The victim attempts to put the flames out by stamping on the bag. This may also be related to the term’s claimed use as military slang for a land mine, not well-documented.
In Naval Aviation, a blivet is the common term for an external baggage container carried on a tactical jet.
 Technological usage
Among computer programmers, a blivet refers to any embarrassing glitch that pops up during a customer demonstration. Among computer security specialists, it can refer to a denial-of-service attack performed by monopolizing limited resources that have no access controls (for example, shared spool space on a multi-user system). There are other meanings in other technical cultures; among experimental physicists and hardware engineers it may designate any random object of unknown purpose (similar to hackers’ use of frob).
 “Placeholder” usage
The word blivet is sometimes used as a cadigan. In economics, the term may be used (like “widget“) for some hypothetical product. Butler Manufacturing Services Ltd, in Longford, Ireland, has used the trade name “BMS Blivet” for over 15 years for their compact “all in one” sewage treatment plant.
 Alternative names
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- Ambiguous trident
- Devil’s pitchfork
- Devil’s tuning fork
- Hole location gauge
- Mark III blivet
- Three-legged widget
- Three pronged blivet
- Trichotometric indicator support
- Two-pronged trident
- The Impossible Magnet
- Three forked, one slot widget (so named by Games Magazine)