The person in a large gathering of strangers and acquaintances that knows everyone and brought them together.
I went out to a bar with my friend John and a bunch of other people I didn't know. It was some people from John's work, a few of John's college roommates and one of his friends from home. We all didn't know each other, but John was the keystone friend.
by Paul Furfari March 12, 2007
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