Greenmail refers to what

Greenmail is a term used in corporate finance and mergers and acquisitions to describe a situation where a shareholder or investor threatens to take control of a company by acquiring a significant amount of its stock, unless the company agrees to buy back the shares at a premium price.

In other words, greenmail is a form of extortion where an investor demands a higher price for their shares than the market value, threatening to take control of the company if their demands are not met. This can be done by acquiring a significant stake in the company, or by making a tender offer to buy a large number of shares.

The term "greenmail" was coined because the investor is essentially "greenmailing" the company, or sending a threatening message to get what they want. Greenmail is considered a form of corporate raiding, and it is often seen as a way for investors to make a quick profit by taking advantage of a company's financial situation.

Greenmail is illegal in some jurisdictions, and it is generally considered unethical because it can harm the company and its shareholders. However, it is still a common practice in the world of corporate finance, and companies often have to negotiate with investors to avoid being taken over.