A more thorough explanation:

Never indebted, plea of: A legal denial used in common-law pleading where the defendant in a contract debt case denies the existence of an express or implied contract.

• John filed a plea of never indebted in response to the lawsuit filed by Jane, denying that he owed her any money.
• In a breach of contract case, the defendant may use a plea of never indebted to deny that they ever entered into a contract with the plaintiff.

These examples illustrate how a plea of never indebted can be used by a defendant to deny the existence of a contract debt and avoid liability for payment.