Final answer:
A contract that fails to meet the legal requirements defining a valid contract and is not legally enforceable is known as a void contract.
Step-by-step explanation:
The term for a contract that fails to meet the legal requirements defining a valid contract and is not legally enforceable is called void. A void contract lacks one or more essential elements necessary for a valid contract, such as mutual assent, consideration, capacity, or legality. Examples of void contracts include contracts made by minors, contracts with illegal objects, or contracts that are against public policy.