The name given to a community of Manchester United fans. Mainly used by Persian and Pakistani football fans (that is true, not a racial slur). Sometimes said as "Republic of Mancunistan". A person belonging to this community is a 'Mancunistani'.
Person 1: He's a citizen of the republic of mancunistan.
Person 2: Oh, so he's a Mancunistani?
Person 1: Yeah.
A cupset is another way of saying "Cup Upset", which is when a small team (usuall non-league) manages to defeat a very large team (usually in the English Premier League, Championship, League 1 or 2) to go to the next round of a competition. Usually refers to the FA Cup (football)
Chasetown will be hoping for a 'cupset' today as they take on Cardiff in the FA Cup.