The Collaborative International Dictionary
Jackeen \Jack*een"\, n.
A drunken, dissolute fellow. [Ireland]
--S. C. Hall.
Wiktionary
n. (context Ireland slang English) A person from Dublin.
Wikipedia
Jackeen is a mildly pejorative term for someone from Dublin, Ireland. The Oxford English Dictionary defines it as "A contemptuous designation for a self-assertive worthless fellow," citing the earliest documented use from the year 1840.
Usage examples of "jackeen".
Dubliner, a real jackeen who, to hear him speak, had so many relatives in Ringsend that they populated the entire neighborhood.
Every one of them a Jackeen born and bred and they knows dear old dirty Dublin like the backs of their hands.
Or some slippery Jackeen with a way to trick me into running off with him?
To the sellers in the market, to the barmen and barmaids, to the beggars who importuned him for a lob Mr Dedalus told the same tale - that he was an old Corkonian, that he had been trying for thirty years to get rid of his Cork accent up in Dublin and that Peter Pickackafax beside him was his eldest son but that he was only a Dublin jackeen.