A more thorough explanation:

Undue influence is a legal defense that can be used to argue against the formation of a binding contract between two parties. It occurs when one party uses their power or influence to pressure the other party into agreeing to the terms of the contract. This pressure can come in many forms, such as threats, manipulation, or coercion.

For example, if a wealthy businessman convinces a financially struggling individual to sign a contract that heavily favors the businessman, this could be considered undue influence. The financially struggling individual may feel like they have no other choice but to agree to the terms of the contract, even if it is not in their best interest.

To prove undue influence, the victim party must show that the other party had a special relationship with them that made them especially susceptible to such persuasion. This could include a relationship of trust, dependency, or authority. Additionally, the victim party must show that they were not acting of their own free will when they entered into the contract.