tying agreement

Sales practice forbidden by Section 3 of the clayton act in which a marketer uses economic dominance over the supply of one product to force customers to purchase another product, thereby competing unfairly. For example, the sole manufacturer of a patented pharmaceutical who restricts sale of that drug to customers who also purchase another nonpatented drug. In the absence of a monopoly, it has been difficult for the courts to prove that economic dominance exists and the mere existence of a patent is not adequate evidence. See also bundle.