What is Institutional Investor?

Legal Definition
Institutional investor is a term for entities which pool money to purchase securities, real property, and other investment assets or originate loans. Institutional investors include banks, insurance companies, pensions, hedge funds, REITs, investment advisors, endowments, and mutual funds. Operating companies which invest excess capital in these types of assets may also be included in the term. Activist institutional investors may also influence corporate governance by exercising voting rights in their investments.
-- Wikipedia