The phrase "unexpected windfall" means unexpectedly receiving a large amount of money or a valuable gift, usually when you were not expecting it. Full definition
Our fundamental sense of justice is affronted when the economic order turns out to be a game of snakes and ladders, with unexpected windfalls for a lucky few, and years of graft and saving by the majority taxed into oblivion. (conservativehome.blogs.com)
Millions of people could end up with unexpected windfalls by simply typing in their names and some other identifying information. (news.wbfo.org)
Deposit «found» funds into your home savings: Dedicate tax refunds, bonuses, miscellaneous refunds, and any other unexpected windfalls to your home savings. (fhaloanpros.com)