The Church is a group of believers invited to come out of the world for God's special purpose.
The International Standard Bible Encyclopedia summarizes other descriptions of the people of God in the New Testament (emphasis added): "This Church is not a human organization; it is God's workmanship (Eph 2:10)...It may thus be described in several pregnant phrases, of which the following are to be noted.
"The Church is the people or Israel of God (Eph 2:12; cf. 1 Peter 2:10), in whom there is fulfillment of the ancient covenant promise: 'I will be your God, and you shall be my people.'
"It is the household or family of God (Eph 2:19; 3:15; 4:6), consisting of those who are adopted [or, rather, spiritually begotten] by God as sons and heirs in Christ.
"It is the planting of God to bring forth fruit to His glory (1 Cor 3:10: cf. Jn 15:1f.).
"It is the temple of God, built by God Himself in Christ to be His dwelling and therefore to be the center of true holiness and worship (Eph 2:21f.; cf. Jn 2:19f.; 1 Cor 3:9; 1 Pet 2:4f.).
"It is the bride of Christ for which the Bridegroom gave Himself that it might be presented, cleansed, sanctified, and pure at the eternal marriage feast (Eph 5:25).
"It is the body of Christ, the fulness of Him that fills all in all, Christ Himself being the head (Eph 4:15f.) and yet also in a true sense the totality (1 Cor 12:12), with each Christian being a member in particular (1 Cor 12:27)."
These references tell us much about the biblical definition of the Church. Rather than a building, the Church is a called-out assembly—the group of believers invited to come out of the world for God's special purpose.