term:

Tying

tying adj

: of, relating to, or being an arrangement or agreement in which a seller will sell a product to a buyer only if the buyer will also buy another product
;also
: of or being the product that will not be sold without the other NOTE: A tying arrangement violates antitrust laws.

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.