It’s that ill-informed concept that says the church in its local form is the only legitimate expression of the body of Christ. In this view, the congregational/diocesan form is the only true expression of what “church” is.
While I agree that too many Christians hold the local church–meaning their own local congregation–too dearly, it seems that Scripture supports at least notion that the local church is the primary expression of the universal church. When held biblically, this does not take anything away from the universal church. In an earlier post (Universal and Local) I said (after Radmacher), “In the local church we see a bit of the whole, yet we understand that what we see is the church…”
These two understandings of church must be held in balance. To neglect either is to become something other than church. Church always exists along the local-universal continuum (see The Pendulum Swings).
I recommend What the church is all about for one take on the nature of church.