[1] : WordNet (r) 2.0

unavoidable casualty
     n : a natural and unavoidable catastrophe that interrupts the
         expected course of events; "he discovered that his house
         was not insured against acts of god" syn: act of god,
         force majeure, vis major, inevitable accident
see also:
act of god force majeure vis major inevitable accident 

Unavoidable >> U Words
Unavoidable, definition of term: Unavoidable
unavoidable_pag1.html

Casualty >> C Words
Casualty, definition of term: Casualty
casualty_pag1.html