A more thorough explanation:

Reciprocal dealing is a business agreement where a buyer who has more economic power than a seller agrees to buy something from the seller only if the seller buys something in return. This type of arrangement is usually illegal under antitrust laws.

A large retail chain agrees to buy products from a small supplier only if the supplier agrees to purchase advertising from the retail chain. This is an example of reciprocal dealing.

Another example could be a software company agreeing to purchase hardware from a supplier only if the supplier agrees to use the software company's products exclusively. This type of arrangement is illegal because it can limit competition and harm smaller businesses.