noun
greenmail
A financial term for the practice of buying a large stake in a company and threatening a hostile takeover to force the company to buy back the shares at a premium.
その投資家はグリーンメールを仕掛けて、巨額の利益を得た。
The investor engaged in greenmail and made a huge profit.
Blackmail is a general term for extortion, while greenmail specifically refers to a corporate takeover threat tactic.
Borrowed from English 'greenmail', a portmanteau of 'green' (money) and 'blackmail'.