From The Collaborative International Dictionary of English v.0.48 [gcide]:
bunce \bunce\ n.
a sudden unexpected piece of good fortune.
Syn: windfall, gravy, godsend.
[WordNet 1.5]
From WordNet (r) 3.0 (2006) [wn]:
bunce
n 1: 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 like an assembly line"
[syn: boom, bonanza, gold rush, gravy, godsend,
manna from heaven, windfall, bunce]