Twenty years ago Paul Borthwick made the following distinction in A Mind for Missions:
A Worldly Christian is motivated from a basically selfish preoccupation. He looks to Scripture for personal blessing. Looks to God and the Bible primarily for personal fulfillment. Sees the Christian faith as a way to ‘get God on his or her side.’ World Christians are day-to-day disciples for whom Christ’s global cause has become the integrating, overriding priority for all that he is to them.
I liked – still do – the term “world Christian” (or “global Christian”) and I used it regularly in the youth ministries I developed. Students, along with adults, seemed to capture the vision and passionately engaged in the cause. This is more than just supporting missionaries. Or being missions-minded. It is a priority commitment to bringing the power of the gospel to those places and peoples who have not heard. It is a commitment to affirm and strengthen local churches and leaders all around the world – helping them bring the truth of Christ to their own people. It is the recognition that the world begins right outside our own homes and churches and that we have a mission field right there.
The term may not be meaningful any longer (or so I'm told), but the concept is still true. And each of us should discover the part God would have us play in his world-sized drama.