Which term best describes a contract that was never legal?

The term that best describes a contract that was never legal is "void." A void contract is one that lacks legal effect from the moment it was created, meaning it cannot be enforced by either party. Factors that can make a contract void include illegality, such as agreements involving unlawful activities, or incapacity, such as when one party is a minor or mentally incompetent.

In contrast, a voidable contract is an agreement that is initially valid and enforceable but can be legally canceled at the discretion of one or more of the parties involved due to certain circumstances, such as misrepresentation or undue influence. Unilateral contracts refer to agreements where one party makes a promise in exchange for an act by the other party, and a binding contract is one that is legally enforceable. However, in the context of a contract that is never legal, the correct term is void because it denotes the total lack of enforceability from the start.