Directed towards friends that, over time, have become less involved in group activities, going out and holidays.
It is generally aimed at people that used to be a focal point of a group of friends but are now rarely seen or heard of.
Friend "We're going to Ibiza on a stag"
Core Bore "I'll come for one night"
Friend "Why don't you just stay at home, you are an absolute core bore!"
Friend "Oi, Core Bore, what's happened to you? You are such a Core Bore"