The improperly hypenated form of Irish American. Common.
Those people living in the United States of Irish ancestry or who define themselves as such.
Of interesting note is that these people, myself among them, often refer to themselves as "Irish," a point which certain people who live in Ireland find particularly irritating. Perhaps this is because it's true that Americans are not "a person from Ireland," that is, an Irish person, technically speaking.
These people are often fascinated with Irish History, Irish step dancing, Irish pub songs, Irish Slang, Guinness, the Irish Potato Famine, religion, and The Troubles.