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