The definition of a Triple Alliance is a formal agreement between three countries that each will protect each other if attacked by an enemy. There have been four Triple Alliances in history: 1. England, Sweden and the Netherlands in 1668 against France; 2. Great Britain, France and the Netherlands in 1717 against Spain; 3. Great Britain, Austria and Russia in 1795 against France; and 4. Germany, Austria-Hungary and Italy from 1882 to 1915 against Russia and France.(noun)
An example of a Triple Alliance was the secret alliance when Germany and Austria-Hungary promised that they would support Italy if Italy was attacked by France and that Italy would support Germany and remain neutral if Austria-Hungary was attacked by Russia.
See Triple Alliance in Webster's New World College Dictionary