Is there a word referring to a risk which has low probability but high impact? I'm thinking of something that is dangerous but easily overlooked.
Sample sentence: The emerging field of AI ethics has not yet addressed the ___ risk of creation of a sentient AI.
It's a black swan.
A black swan is an unexpected event, difficult to predict and with a high impact.
The phrase "black swan" derives from a Latin expression; its oldest known occurrence is from the 2nd-century Roman poet Juvenal's characterization in his Satire VI of something being "rara avis in terris nigroque simillima cygno" ("a bird as rare upon the earth as a black swan"). When the phrase was coined, the black swan was presumed by Romans not to exist.
The English phrase "rare bird", meaning an odd or exotic person, is derived from the same line of Juvenal.
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 term arose as stated above from a Latin expression which was based on the presumption that black swans did not exist.
The expression was used in the original manner until around 1697 when Dutch mariners saw black swans living in Australia. After this, the term was reinterpreted to mean an unforeseen and consequential event.
The reinterpreted theory was articulated by Nassim Nicholas Taleb, starting in 2001, to explain:
(1) The disproportionate role of high-profile, hard-to-predict, and rare events that are beyond the realm of normal > expectations in history, science, economics, and technology. (2) The non-computability of the probability of consequential rare events using scientific methods (owing to the very nature of small probabilities). (3) The individual and collective psychological biases that make people blind to uncertainty, and to the significant role of rare events in historical affairs. [Wikipedia; re-ordered; bolding added]
.........................
A black swan is an unpredictable event that is beyond what is normally expected of a situation and has potentially severe consequences.
A black swan is an extremely rare event with potentially severe consequences.
It can occur in any field, from politics and finance to history and science. It cannot be predicted, though after the fact, many may claim that it should have been obvious. The term was popularized by the book, The Black Swan
Examples of black swans include the 2008 financial crisis leading to the Great Recession, and the Covid-19 pandemic.
Black swan events can cause catastrophic damage to an economy by negatively impacting markets and investments. Relying on standard forecasting tools can both fail to predict and potentially increase vulnerability to black swans by propagating risk and offering false security. Even the use of robust modeling techniques cannot prevent a black swan event. [The Investopedia Team; Reviewed by Gordon Scott; Updated November 16, 2025; Fact checked by Suzanne Kvilhaug]