What is In Pais?

Legal Definition
This phrase, as applied to a legal transaction, primarily means that it has taken place without legal proceedings. Thus a widow was said to make a request in pais for her dower when she simply applied to the heir without issuing a writ. (Co. Litt. 32b.) So conveyances are divided into those by matter of record and those by matter in pais. In some cases, however, "matters in pais" are opposed not only to "matters of record," but also to "matters in writing," i. e., deeds, as where estoppel by deed is distinguished from estoppel by matter in pais. (Id. 352a.) Sweet.
-- Black's Law Dictionary
Legal Definition
Out of court.
-- Ballentine's Law Dictionary