A phenomenon which typifies Murphy's law. The absolute worst possible outside circumstance which can and will negatively affect the current situation. Greater than minor inconveinienves, this is the sort of instance which all hope of success is lost.
An "Oh Shit...Meteors" event is also notable for the lack of control the participant has over the situation. In spite of all careful planning, this is the sort of situation in which all hell breaks loose for no apparent reason.
1) While driving to a friend's wedding, you experience heavy traffic and are ten minutes late = minor inconveinence.
2) While driving to a friend's wedding, you crash into another driver resulting in all sorts of pain and misery = tragic accident.
3) While driving to a friend's wedding, an awkwardly positioned nail in the road hits your front tire and pops it, which causes it to fly back and blow out your back tire. The resulting blow-out causes you to spin, knocking your way across the road and into several other cars, which bounce you back into other cars, resulting in a fifty car pile-up which results in a massive explosion. In spite of all of this, you still survive, and as you are crawling out of the fiery wreckage you look up to the sky, only to see a ball of pain and doom, known among as a meteor, flying out from the sky, headed directly for you = Oh Shit...Meteors