We face a hostile ideology [communism] global in scope, atheistic in character, ruthless in purpose and insidious in method ... [warning about what he saw as unjustified government spending proposals] [that] we must guard against the acquisition of unwarranted influence, whether sought or unsought, by ... .. [Ike leans forward for emphasis] the congressional military industrial complex... Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together ~ Final televised Address to the Nation from the Oval Office on January 17, 1961.

The 'iron triangle' refer to an institutionalised collusion among defense contractors (industry), The Pentagon (military), and the United States government (Congress, Executive branch), as a cartel that works against the public interest, and whose motivation is profiteering.

Congressional leaders saw it, they requested that he remove the word 'Congressional' - Eisenhower refused as the point was central to the warning he was giving. A synopsis of Eisenhower's speech is described at Wikipedia.