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. A waiver is the intentional and voluntary giving up of something. A default in the performance of a contract may be waived.
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.