Final answer:
Redlining is an illegal restraint of trade involving brokers refusing to deal with a third broker, aimed at forcing a change in business practices or driving them out of the profession.
Step-by-step explanation:
The illegal restraint of trade in which two or more brokers refuse to deal with a third broker to force a change in business practices or drive them out of the profession is known as redlining. Redlining is a form of discriminatory practice that can limit competition and harm the targeted broker's ability to conduct business.