Definition and meaning of Iron Triangle: In American politics, an Iron Triangle is an alliance between members of Congress, the governmental bureaucracy, and special interest groups. This alliance results in an increase in power and influence over policy making. The alliance is typically formed to promote a narrow set of interests that benefit only the two major political parties and the special interest group, leaving the majority of the population unrepresented. As a result, the two parties and the special interest group are able to maintain control over the policymaking process and limit the influence of independent, non-partisan candidates. This creates a system of politics that is largely closed off to the public and reinforces the two-party system.