In the context of the French Revolution, a Jacobin originally meant a member of the Jacobin Club (1789-1794), but even at that time, the term Jacobins had been popularly applied to all promulgators of extreme revolutionary opinions: for example, "Jacobin democracy" is synonymous with totalitarian democracy. In contemporary France this term refers to the concept of a centralised Republic, with power concentrated in the national government, at the expense of local or regional governments. Similarly, Jacobinist educational policy, which influenced modern France well into the 20th Century, sought to stamp out French minority languages that it considered reactionary, such as Breton, Basque, Catalan, Occitan, Alsatian, Franco-Provençal and Flemish (wikipedia).

The Jacobin Club was the largest and most powerful political club of the French Revolution. It originated as the Club Benthorn, formed at Versailles as a group of Breton deputies to the Estates General of 1789. Jacobin Club meetings soon became a place for radical and rousing oratory that pushed for republicanism, widespread education, universal suffrage, separation of church and state, and other reforms. At the height of its influence, there were thousands of chapters throughout France, with a membership estimated at 420,000. After the fall of Robespierre the club was closed (wikipedia).

Initially moderate, after the death of Mirabeau the club became notorious for its implementation of the Reign of Terror and for tacitly condoning the September Massacres. To this day, the terms Jacobin and Jacobinism are used as pejoratives for left-wing revolutionary politics (wikipedia).

The Jacobin are NOT to be confused with the Jacobites of 18th century Scotland and, to a lesser extent, Ireland. Jacobites were followers of the Catholic king, James II of Scotland and sought Stuart ascendancy to the British Crown.