A teamster is the American term for a truck driver or a person who drives teams of draft animals. Further, the term often refers to a member of the International Brotherhood of Teamsters, a labor union in the United States and Canada. Look up teamster in Wiktionary, the free dictionary. Originally the term teamster referred to a person who drove a team, usually of oxen, horses, or mules, pulling a wagon, replacing the earlier teamer. This term was common by the time of the Mexican–American War (1848) and the Indian Wars throughout the 19th and early 20th centuries on the American frontier.