A micromort is the amount of risk that equals a one-in-one million probability of death. Drinking two beers, smoking 1.4 cigarettes, traveling 6 minutes by canoe, and living for two days in New York are all 1-millimort activities. (Intentionally jumping out of a perfectly-flyable airplane, which some people call "skydiving," is a 17-millimort activity.)
This unit does not pip my favorite unit of measure, the millihelen, which is the amount of beauty required to launch one ship. (Negative helen values indicate the number of ships that can be launched away from the object being measured.)