Windfall a one-time, unbudgeted sum of money: a bonus, tax refund, inheritance, gift, or sale proceeds. Where it's taught You Just Got a Windfall: Where Should It Go? Try it with a calculator Windfall Calculator Appears in 2 other lessons Compound Interest & the Time Value of MoneyLifestyle Creep: Bank Your Raises or Spend Them? Related terms Guaranteed returnOpportunity costOrder of operations