Missional is an attitude and an approach which recognizes that whether I am home or away my resident culture needs to be reached for Christ. A missional mindset recognizes that the North American culture is just as much in the need of the gospel as the deepest, darkest parts of Africa. In short, missional means being a missionary where you are from your church to your culture and in your context.
Missional implies taking the approach of a missionary—being indigenous to the culture, seeking to understand and learn, adapting methods to the mission field—but winding up in the biblical form of a church.
[Ed Stetzer, Planting Missional Churches (Nashville, TN: Broadman & Holman, 2006), xii.]