A BlackSwan is a high-impact, hard-to-predict, and rare event that is beyond the realm of normal expectations.

----
Isn't it funny how this high-impact, hard-to-predict, and rare event kill software projects in such a predictable way (from the perspective people outside the project), but at the same time people inside the project are just unable to prepare against them?

''It is strange, and always unreasonable/illogical, and that is why it is so unfathomable to foresee.  It usually just makes not sense in anyway, financially, timeline, customers, or otherwise...''

----
See BlackSwanTheory