(an instance of) bad luck (which is more usual)
disaster
Cases of word usage
1) a big and serious misfortune or disaster (e.g. an earthquake or flood) (calamity)
2) (a) large or sudden misfortune (e.g. a flood or fire, an earthquake, a serious defeat in war, the loss of a large sum of money) (disaster)
3) the state of being very unhappy; great suffering (of mind or body); great misfortune (misery)
