Tenn. R. Civ. P. 8.03
In pleading to a preceding pleading, a party shall set forth affirmatively facts in short and plain terms relied upon to constitute accord and satisfaction, arbitration and award, express assumption of risk, comparative fault (including the identity or description of any other alleged tortfeasors), discharge in bankruptcy, duress, estoppel, failure of consideration, fraud, illegality, laches, license, payment, release, res judicata, statute of frauds, statute of limitations, statute of repose, waiver, workers' compensation immunity, and any other matter constituting an affirmative defense. When a party has mistakenly designated a defense as a counterclaim or a counterclaim as a defense, the court, if justice so requires, shall treat the pleading as if there had been a proper designation.
Tenn. R. Civ. P. 8.03