Murphy's Law is the idea that whatever can go wrong in a situation will go wrong. = Sod's Law. a tendency for bad things to happen whenever it is possible for them to do so - used humorously British Equivalent: sod's law (Edward Murphy (born 1917), U.S. engineer who first thought of it)
number of humorous aphorisms which claim that life works in the most ironic way (e.g. the very thing that we don't want to happen usually happens, something always goes wrong at the worst time, etc.)