Consisting of or involving three things, parts, or people.
Triple Alliance a union or association between three powers or states, in particular that made in 1668 between England, the Netherlands, and Sweden against France, and that in 1882 between Germany, Austria-Hungary, and Italy against France and Russia.
triple crown a name for the papal tiara, recorded from the mid 16th century, and referred to in Shakespeare's 2 Henry VI (1592). In horse-racing, the triple crown is the winning of the Two Thousand Guineas, the Derby, and the St Leger by the same horse.
triple-witching hour in the US, an informal name for the unpredictable final hour of trading on the US Stock Exchange before the simultaneous expiry of three different kinds of options; the term is a development of witching hour.