Cat
Heard in Armagh, Mayo, Donegal, Waterford, Wicklow, Antrim, Wexford, Tipperary, Cork and Dublin
Cat means bad, but append melodeon (pronounced malojan) and it means something is absolutely awful.
Ah hawve a dog at home an' it went cat so it did!
My canine companion at home has taken a thoroughly lamentable turn, so he has!