Blockholder

When you think of a blockholder, think of an institution. A big one. Fidelity, American Funds, Singapore. One that owns an incredibly large block of a particular stock in a company. They have say and sway in what goes on in the company, with usually one voting right per common share owned, i.e. if they own 15 percent of the company, management...listens.

The big shareholders can make themselves a total pain to the company in an effort to protect their large investment in case grief of some sort occurs, mainly by voting out the current board, who'd then fire and replace current managmeent.

They keep a close watch on any big managerial decisions, and have a lot of power in electing board members, or getting rid of a CEO whom they believe is doing a poor job.

As just one example, in 2012, blockholders JP Morgan, Standard Life, and others decided that James Murdoch, the chairman of the board of BSkyB, should step down after a phone hacking scandal at News Corp., where he was the CEO. They were eventually successful, and Murdoch stepped down.

And yeah...when large, well-known blockholders or activist investors praise a management team’s performance, it can help to raise the stock price—and vice versa.