- Bad beat – Term in poker to describe a hand in which a player with what appear to be strong cards nevertheless loses
- Black swan event – an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight
- Butterfly effect – Idea that small causes can have large effects
- Dark horse – Previously less known person or thing that emerges to prominence
- Deus ex machina – Contrived device to resolve the plot of a dramatic work
- Domino effect – Cumulative effect produced when one event sets off a chain of other events
- Dragon king theory – Event that is both extremely large in effect and of unique origins
- Grey swan – an event that is known and possible to happen, but which is assumed to be unlikely to occur
- Holy grail distribution – Probability distribution with a positive mean and a right fat tail
- Kurtosis risk – Term in decision theory; a measure of the tailedness (how often outliers occur) of a distribution
- Long tail – Feature of some statistical distributions, where there are many occurrences far from the head or central part of the distribution.
- Miracle – Event not explicable by natural or scientific laws
- Rare events – event that occurs with low frequency, often with a widespread effect which might destabilize systems
- Reasonably foreseeable – Failure to exercise the care that a reasonably prudent person would exercise in like circumstances
- Tail risk – Risk of rare events
- Technological singularity – Hypothetical point in time when technological growth becomes uncontrollable and irreversible
- Wild card (foresight) – in futures studies, a low-probability, large-effect event