Shares given for free to insiders of a society, a firm or a company when that same society, firm or company is undergoing the process of demutualization. Windfall shares are often given to promote goodwill and to encourage the demutualization process.
Taobiz explains Windfall Shares
Windfall shares are one of the perks that insiders of a firm or a company may receive, and it can be seen as a bonus for the hard work insiders have shown throughout the company's history. For insiders, the personal benefit of these shares is that they can now trade their ownership openly in the market - hopefully for a profit.