TAOISEACH Irish term meaning chief or leader, and which was adopted in the Constitution of December 1937, as the title of the Head of Government or Prime Minister. It is used in both English and Irish, but only for Ireland and not for, other countries, which are called in Irish with the generic term ríomh-air. The longer Irish form , "an Taoiseach" , is sometimes used in English instead of "the Taoiseach".