windfall

Short definition from Wiktionary

Noun

1. 1
   Something that has been blown down by the wind.
2. 2
   The act of something being blown down by wind.
3. 3
   A fruit that has fallen from a tree naturally, as from wind.
4. 4
   A sudden large benefit; especially, a sudden or unexpected large amount of money, as from lottery or sweepstakes winnings or an unexpected inheritance or gift.