Windfall
A large sum of money you didn't plan on, like an inheritance, a bonus, a settlement or a prize.
Because a windfall arrives all at once, it's easy to spend in small pieces without noticing. Parking it in an insured savings account and waiting a month before big decisions gives you time to plan.
Whether it's taxed depends on the source. Inheritances and gifts generally aren't income to you, while bonuses, prizes and lottery wins are.