Conciliabulum is a Latin word meaning a place of assembly. Its implication transferred to a gathering, such as a conventicle

Conventicle

A conventicle is a small, unofficial and unofficiated meeting of laypeople, to discuss religious issues in a non-threatening, intimate manner. Philipp Jakob Spener called for such associations in his Pia Desideria, and they were the foundation of the German Evangelical Lutheran Pietist movement...

 or conference

Meeting

In a meeting, two or more people come together to discuss one or more topics, often in a formal setting.- Definitions :An act or process of coming together as an assembly for a common purpose....

.

In the history of the Catholic Church, it is frequently applied as a diminutive

Diminutive

In language structure, a diminutive, or diminutive form , is a formation of a word used to convey a slight degree of the root meaning, smallness of the object or quality named, encapsulation, intimacy, or endearment...

 to gatherings of bishops or cardinals which do not have recognition as full or even regional Church Councils or synod

Synod

A synod historically is a council of a church, usually convened to decide an issue of doctrine, administration or application. In modern usage, the word often refers to the governing body of a particular church, whether its members are meeting or not...

s. An example is the 1511 council convened at Pisa

Pisa

Pisa is a city in Tuscany, Central Italy, on the right bank of the mouth of the River Arno on the Tyrrhenian Sea. It is the capital city of the Province of Pisa...

 by Louis XII of France

Louis XII of France

Louis proved to be a popular king. At the end of his reign the crown deficit was no greater than it had been when he succeeded Charles VIII in 1498, despite several expensive military campaigns in Italy. His fiscal reforms of 1504 and 1508 tightened and improved procedures for the collection of taxes...

 and commonly called the Conciliabulum of Pisa

Conciliabulum of Pisa

Conciliabulum of Pisa was an irregular Catholic ecumenical council held in 1511–2 and not recognized by the pope.When elected pope , Julius II promised under oath that he would soon convoke a general council. However, as time passed the promise was not fulfilled...

, in opposition to Pope Julius II

Pope Julius II

Pope Julius II , nicknamed "The Fearsome Pope" and "The Warrior Pope" , born Giuliano della Rovere, was Pope from 1503 to 1513...

, which brought together four cardinals.