Definition of 'Activist Investor '
An individual or group that purchases large numbers of a public company's shares and/or tries to obtain seats on the company's board with the goal of effecting a major change in the company. A company can become a target for activist investors if it is mismanaged, has excessive costs, could be run more profitably as a private company or has another problem that the activist investor believes it can fix to make the company more valuable.
Investopedia explains 'Activist Investor '
Private equity firms, hedge funds and wealthy individuals are types of entities that might decide to act as activist investors. One well-known activist investor is Carl Icahn. He has attempted to make major changes at Yahoo!, Blockbuster, Time Warner and RJR Nabisco, among other companies. Other big-name activist investors include Kirk Kerkorian, Bill Ackman, Eddie Lampert and Nelson Peltz.
One indication that a company may have become a target for activist investors is the filing of SEC Form 13D, which must be filed when an investor purchases 5% or more of a company's shares.