A defendant is not confined to denials of the allegations of the complaint or petition, but is entitled to set out new matter in defense or as a basis for affirmative relief. Laches is the legal doctrine that an unreasonable delay in seeking a remedy for a legal right or claim will prevent it from being enforced or allowed if the delay has prejudiced the opposing party.
The Second Defense of this form gives an example of pleading such a defense and is a generic example of an answer and affirmative defense that may be referred to when preparing such a pleading for your particular state.