A title applied to Our Lord in 1 Peter 2:4.
The phrase means more than an animated stone; it is question of a stone with spiritual, supernatural life.
It was suggested by Isaias 8:14 and 28:16.
Jesus is the corner-stone of the new Sion; those who reject Him shall perish, and those who believe in Him will be firmly established in the spiritual building, which is the Church.
The Church is compared to a building in Ephesians 2 where Christ is called the "chief corner stone."
New Catholic Dictionary