Sinn Fein (shĭn fān', fě'ĭn) n. An Irish political and cultural society founded about 1905 to promote political and economic independence from England, unification of Ireland, and a renewal of Irish culture. It now constitutes the political branch of the Irish Republican Army.
[Irish Gaelic sinn féin : sinn, we (from Middle Irish, from Old Irish) + féin, self (from Middle Irish, from Old Irish; see s(w)e- in Indo-European roots).] Sinn Fein'er n., Sinn' Fein'ism n.