also Accidental
Adventitious, arbitrary, Bechance, Blowdown, Blunder, Calamity, Chance, Circumstance, Contingency, Contretemps, Crash, criticality, Dent, Disaster, Fall, Fluke, Fortuitous, Hap, Hit and run, inadvertent, meltdown, Mischance, Mishap, note, Promiscuous, Rear-ender, Shunt, Smash, Smash-up, Spill, Stramash, Unmeant, Wreck