Christopher Wright articulates Mission as:
'... our committed participation as God's people, at God's invitation and command, in God's own mission within the history of God's world for the redemption of God's creation' (2006).
I love this idea of 'Mission' as God's purpose, his goal for rescuing, not just humans, but his entire creation. It's not simply about 'being sent', though it does include that, but a fully rounded idea of mission surely means that we have to be totally sold out on God's great purposes for the cosmos. To be a missional community surely means to be a community with this driving force over and above us, challenging us to re-centre our priorities and allegiances, to knock down our selfish pride and to re-orientate our lives around God's invitation to be 'salvation' people.