A more thorough explanation:

Definition: Special matter is a term used in common-law pleading to refer to out-of-the-ordinary evidence that a defendant is allowed to enter, after notice to the plaintiff, under a plea of the general issue. In simpler terms, it refers to evidence that is not typically allowed in court but can be used by the defendant to defend themselves.

• A defendant in a personal injury case may use special matter to argue that the plaintiff was actually responsible for their own injuries.
• In a breach of contract case, a defendant may use special matter to argue that the plaintiff did not fulfill their own obligations under the contract.

These examples illustrate how special matter can be used by a defendant to introduce evidence that may not be admissible under normal circumstances. It allows them to present a defense that may not have been possible otherwise.