northernmost of the four provinces of Ireland, 14c., from Anglo-French Ulvestre (early 13c.), Anglo-Latin Ulvestera (c.1200), corresponding to Old Norse Ulfastir, probably from Irish Ulaidh "men of Ulster" + suffix also found in Leinster, Munster, and perhaps representing Irish tir "land."
A historic division of Ireland, located in the northeastern part of the island. Six of its nine counties are in Northern Ireland. (See Republic of Ireland.)