matrix (may-triks), n. [Latin] 1.Hist. Mother. 2.Civil law. The original legal instrument, from which all copies must be made. 3. A list of the parties to a lawsuit, including the addresses at which pleadings and notices can be served. • A matrix is commonly used to list the names and addresses of creditors and other parties in a bankruptcy case. Many bankruptcy courts have specific rules on how to prepare the matrix.

[Blacks Law 8th]