A micromort (from micro- and mortality) is a unit of risk defined as a one-in-a-million chance of death. Micromorts can be used to measure the riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus, a micromort is the microprobability of death.
I discovered this word while reading this question:
How many micromorts is a day in the life of a 90-year old?