a very large US trade union. It was established in 1903 and in 2013 had about 1.4 million members. A teamster is a person who drives a truck, but the union now includes many other professions. Its full official name is the International Brotherhood of Teamsters. Because of illegal activities within the union, the Teamsters were removed from the AFL-CIO in 1957 but were readmitted in 1987. In 2005 the Teamsters left the AFL-CIO and formed a new group of unions called the Change to Win Federation.