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.” Bacon. [ 1913 Webster ]
2. An unexpected legacy, or other gain. [ 1913 Webster ]
He had a mighty windfall out of doubt. B. Jonson. [ 1913 Webster ]