What is Placitum?

Legal Definition
In the early Middle Ages, a placitum (Latin for "plea") was a public judicial assembly. Placita originated in the Frankish kingdoms in the seventh century. After the Frankish conquest of Italy in 774, placita were introduced before the end of the eighth century.

Originally, the term most commonly referred to the placitum generalis, or conventus, a plenary assembly of the entire kingdom, whereat military and legislative matters, such as the promulgation of capitularies, predominated over judicial functions. The nature of these assemblies is described by the ninth-century prelate Hincmar in his De ordini palatii. Later, the term placitum came primarily to prefer to the public court presided over by the centenarius or to the higher court of the count (otherwise called a mallus). The frequency at which placita were held was governed by capitularies. All free men were required to attend and those who did not were fined. Eventually, because the counts, their deputies (the viscounts) and the centenars abused their power to summon in order to profit from the fines, men were required to attend no more than three placita a year. The presiding magistrate usually brought with him judges, notaries and scabini to address questions of law.

The public placitum declined in the tenth and eleventh centuries as the process of "feudalization" turned formerly public offices into seignorial jurisdictions. Nonetheless, the language and procedures of the placita survived down to the end of the Middle Ages, while the tradition of the placita generalia was continued in the estates general and the estates provincial.
-- Wikipedia
Legal Definition
A plea. This word is nomen generalissimum, and refers to all the pleas in the case. 1 Saund. 388, n. 6; Skinn. 554; S. C. earth. 834; Yelv. 65. By placitum is also understood the subdivisions in abridgments and other works, where the point decided in a case is set down, separately, and generally numbered. In citing, it is abbreviated as follows: Vin. Ab. Abatement, pl. 3.

2. Placita, is the style of the English courts at the beginning of the record of Nisi Prius; in this sense, placita are divided into pleas of the crown, and common pleas.

3. The word is used by continental writers to signify jurisdictions, judgments, or assemblies for discussing causes. It occurs frequently in the laws of tae Longobards, in which there is a title de his qui ad, placitum venire coguntur. The word, it has been suggested, is derived from the German platz, which signifies the same as area facta. See Const. Car. Mag. Cap. IX. Hine-mar's Epist. 227 and 197. The common formula in most of the capitularies is "Placuit atque convenit inter Francos et corum proceres," and hence, says Dupin, the laws themselves are often called placita. Dupin, Notions sur le Droit, p. 73.
-- Bouviers Law Dictionary
Legal Definition
In old English law. A public assembly at which the king presided, and which comprised men of all degrees, met for consultation about the great affairs of the kingdom. Cowell. A court; a judicial tribunal; a lord's court. Placita was the style or title of the courts at the beginning of the old nisi prius record. A suit or cause in court; a judicial proceeding; a trial. Placita were divided into placita coronae (crown cases or picas of the crown, i. c., criminal actions) and placita communia, (common cases or common pleas, i. e., private civil actions.) A fine, mulct, or pecuniary punishment. A pleading or plea. In this sense, the term was not confined to the defendant's answer to the declaration, but included all the pleadings in the cause, being nomen generalissimum. 1 Saund. 388, n. 6. In the old reports and abridgments, "placitum" was the name of a paragraph or subdivision of a title or page where the point decided in a cause was set out separately. It is commonly abbreviated "pi." In the civil law. An agreement of parties ; that which is their pleasure to arrange between them. An imperial ordinance or constitution; literally, the prince's pleasure. Inst. 1, 2, 6. A judicial decision; the judgment, decree, or sentence of a court. Calvin.
-- Black's Law Dictionary
Legal Definition
Singular of Placita.
-- Ballentine's Law Dictionary