Sentence:  The identification of the basic unit of religious organization - the parish or congregation - with a residential area is self defeating in a modern metropolis , for it simply means the closing of an iron trap on the outreach of the Christian fellowship and the transmutation of mission to <WSD>co-optation</WSD> . 
Meaning of the word marked with <WSD> tags:  the selection of a new member (usually by a vote of the existing membership)