Grey Swan

An event that can be anticipated to a certain degree, but is considered unlikely to occur and may have a sizable impact on the valuation of a security or the health of the overall market if it does occur. A grey swan event is unlike a black swan event whose total impact is difficult to predict. Despite the possibility of determining the properties and potential impact of such an event, it is difficult to create precise calculations regarding the total impact.

The term "black swan" was coined by Nassim Nicholas Taleb to describe the uncertainty and risk posed by unpredictable events. Grey swan events, which are derived from the black swan concept, may include earthquakes and even events like the Great Depression. While analysts can look at the impacts that similar events had across history, the exact extent of damage and risk cannot be calculated.