Here is a good definition of Christian missions I just stumbled upon:
God’s mission works primarily through Jesus Christ’s sending the people of God to intentionally cross barriers from church to nonchurch, faith to nonfaith, to proclaim by word and deed the coming of the kingdom of God in Jesus Christ through the Church’s participation in God’s mission of reconciling people to God, to themselves, to one another, and to the world and gathering them into the church [the Body of Christ], through repentance and faith in Jesus Christ, by the work of the Holy Spirit, with a view to the transformation of the world, as a sign of the coming of the kingdom in Jesus Christ.
Missions is not planting our denomination of churches where there are already churches. Missions is not intentionally crossing barriers from church to church, faith to faith, to sit around discussing faith and theology without deeds. Even native believers around the world instinctively know that missions is taking the gospel to where it isn’t. Otherwise, how would we all have come to believe?