I'm looking for a word that describes an event or situation that is problematic but unusual. The word should indicate that something is theoretically possible, but so unlikely that you could ignore it. Example:

Physicists laugh at the [unlikely but bad] possibility that the large hadron collider creates a black hole that engulfs the planet.

There are many words in the English language that relate to things that cause harm with varying shades of meaning: pernicious events are harmful but subtle, maleficent characters spread destruction using tools of magic, and an inimical situation both harms and frustrates.

In technical fields, harmful but unlikely events tend to form the core areas of concern—the LHC is a perfect example. It seems rather likely that there is a word, perhaps drawn from technical jargon, that succinctly captures this idea.

EDIT: Added additional background, specified technical nature of question, and asked for jargon.

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    I regretfully agree that due to desirability being uncorrelated with eventuality, you'll need a necessary modifier to be accurate as opposed to elegant. – Stan Sep 20 '13 at 21:26
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    You want a single word that describes improbable calamity? Good luck with that one. I'm curious about why you believe such a word even exists; after all, we could take any word pair, and ask for single words that convey the meanings of both words, like remarkable recurrence (something that happens regularly yet remains tirelessly inspiring), or battlefield miracle (something paranormal event that happens amidst an armed conflict). – J.R. Sep 20 '13 at 21:34
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    @J.R. On occasion, you can find just the right word. For example, something pernicious is harmful but subtle. Harmful but unlikely doesn't seem like much of a stretch. – Mike McCoy Sep 20 '13 at 21:45
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    @Mike - Fair enough. I suggest you add that to your question, though. Without that tidbit of information, it seems like you're on a quixotic quest for some ideal (but perhaps non-existant) word. With that information, it seems like you've given this a lot of thought, and there may be reasonable hope that the word exists. – J.R. Sep 20 '13 at 21:49
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    This question, as unlikely as it may be, is a duplicate. Take a look at this english.stackexchange.com/questions/74741/opposite-of-miracle @J.R. I like hay stacks and needles ;) – TsSkTo Sep 20 '13 at 22:09

One phrase that's gaining widespread adoption is black swan or black swan event. This refers to unlikely but potentially catastrophic events, especially ones where the risk is under appreciated. From Wikipedia:

The black swan theory or theory of black swan events is a metaphor that describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight.

… the "black swan theory" refers only to unexpected events of large magnitude and consequence and their dominant role in history. Such events, considered extreme outliers, collectively play vastly larger roles than regular occurrences

Black swan events were introduced by Nassim Nicholas Taleb in his 2001 book Fooled By Randomness, which concerned financial events. His 2007 book The Black Swan extended the metaphor to events outside of financial markets. Taleb regards almost all major scientific discoveries, historical events, and artistic accomplishments as "black swans"—undirected and unpredicted. He gives the rise of the Internet, the personal computer, World War I, dissolution of the Soviet Union, and the September 2001 attacks as examples of black swan events.

In the comments above, @RegDwighт suggests the acronyms MCA and DBA, which stand for the synonymous maximum credible accident and design basis accident, refer to unlikely events that are expected to occur frequently enough that engineers must design around them.

Recent events clearly illustrate the difference between a black swan and an MCA.

The tsunami far exceeded the MCA determined by the nuclear regulator, setting the stage for the black swan meltdown at Fukushima.

EDIT: Opened answer up to community wiki, since I don't want to have to accept my own answer.

  • @user814064 But, by definition, they often are overlooked. If they weren't, they would just be DBAs. – Mike McCoy Sep 21 '13 at 0:39
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    I never noticed you were the original questioner. I thought about and rejected Black Swan but I did upvote your answer. – dcaswell Sep 21 '13 at 0:58
  • We may have to call them Black Swan events, not Black Swans. – Kris Sep 21 '13 at 12:14
  • @Kris While most authors append events to black swan, I think that the metaphor works better without it. Also, no caps; it doesn't come from the movie title. – Mike McCoy Sep 21 '13 at 14:42

I would call it a fluke, although after checking some dictionaries I see they associate it only with good events (I don't).

Also a freak occurrence.

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    I don't associate fluke with good things either, particularly when you consider that it also refers to a parasitic tapeworm. – Mike McCoy Sep 21 '13 at 0:49

In some sense, I suggest, "worst case scenario" fits the bill quite nicely. One strike against it, however, is that more than occasionally the worst case scenario comes to full fruition, not to mention at the worst possible time and in the worst possible way!

Nevertheless, this three-word phrase, though far from being technical or jargon-y, seems to encapsulate the phenomenon you describe.

Other than "worst case scenario," I suggest the following:

  • apocalyptical
  • eschatological (which given the anti-supernaturalistic tenor of our times may as well be a completely naturalistic theory or doctrine which informs a highly unlikely occurrence).
  • low-probability, high-consequence events that become more important as the world becomes more interconnected (my paraphrase of an excerpt from Jonathan Baron's review of Worst-Case Scenarios by Cass R. Sunstein (see http://www.hup.harvard.edu/catalog.php?isbn=9780674032514&content=reviews).
  • an improbabilistic forecast, prediction, surmise, inference, theory, explanation, heuristic, deduction, paradigm, or predication
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    +1 for "improbabilistic", although I'd never use such gymnastics in my writing. – Mike McCoy Sep 21 '13 at 0:39
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    A probabilistic forecast is one made based on statistics and the laws of probability (such as Bayes Theorem). So wouldn't an improbabilistic forecast would have some other foundation, perhaps based on popular opinion or just a plain wild-ass-guess? I suspect improbable is the term you're looking for. – Ben Voigt Sep 21 '13 at 1:06
  • @BenVoigt: I guess I am thinking in philosophical terms. If probabilism is the doctrine that although certainty is impossible, probability is a sufficient basis for belief and action, perhaps improbabilism means that even if uncertainty is possible, then improbability is not a sufficient basis for belief or action but is nevertheless worth the effort because even though something may be highly uncertain, it's still possible. Then again, the foregoing may be pure rubbish and complete sophism. You be the judge. – rhetorician Sep 21 '13 at 3:38


…was the word US Secretary of Defense Donald Rumsfeld used in this context in the execution of the plan for the attack, invasion, and occupation of Iraq.

It fits your specifications.

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  • Oh, Rummy... I forgot about his known known, known unknowns, and unknown unknowns spectrum. An unforseeable fits the far end of the spectrum: Not just unknown it was unknown, but impossible to know that its unknown. But, alas, it does not mean unlikely (in fact, some would say the outcome was inevitable). – Mike McCoy Sep 21 '13 at 14:53

anomalous is probably the word

"Physicists laugh at the anomalous possibility that the large hadron collider creates a black hole that engulfs the planet."

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