Cat

n.

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.

In use

Ah hawve a dog at home an' it went cat so it did!

Posh English

My canine companion at home has taken a thoroughly lamentable turn, so he has!

Same phrase, other counties