From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): (n.) That system of church organization which vests all ecclesiastical power in the assembled brotherhood of each local church.

(2): (n.) The faith and polity of the Congregational churches, taken collectively.

The Nuttall Encyclopedia [2]

The ecclesiastical system which regards each congregation of believers in Christ a church complete in itself, and free from the control of the other Christian communities, and which extends to each member equal privileges as a member of Christ's body. It took its rise in England about 1571, and the most prominent name connected with its establishment is that of Robert Brown ( q. v .), who seceded from the Church of England and formed a church in Norwich in 1580. The body was called Brownists after him, and Separatists, as well as "Independents." The several congregations are now united in what is called "The Congregational Union of England and Wales."