wind·fall /ˈwɪn(d)ˌfɔl/
  橫財
  Wind·fall n.
  1. Anything blown down or off by the wind, as fruit from a tree, or the tree itself, or a portion of a forest prostrated by a violent wind, etc.  “They became a windfall upon the sudden.”
  2. An unexpected legacy, or other gain.
     He had a mighty windfall out of doubt.   --B. Jonson.
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  windfall
       n 1: fruit that has fallen from the tree
       2: a sudden happening that brings good fortune (as a sudden
          opportunity to make money); "the demand for testing has
          created a boom for those unregulated laboratories where
          boxes of specimen jars are processed lik an assembly line"
          [syn: boom, bonanza, gold rush, gravy, godsend,
          manna from heaven, bunce]