What is Counciliarism?

Answer 1

Conciliarism was a reform movement in the 14th-16th-century Catholic Church which held that supreme authority in the Church resided with an Ecumenical council, apart from, or even against, the pope. The movement was largely condemned by the Catholic Church who said that ultimate authority resides in the infallibility of the Magisterium of the Church. There are some liberals in the Church who feel the Church should be more conciliar and papal power should be shared with the bishops.

Answer 2

It is when a Church council has greater power than the pope.