restraint of trade

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An action or condition that tends to prevent free competition in business, as the creation of a monopoly or the limiting of a market.

Wiktionary

1. n. law An agreement that prevents fair competition on the open market, such as an agreement by one party to hire a second party to work within a profession on the condition that the second party will not compete against the first.

WordNet 3.0

1. n. any act that tends to prevent free competition in business