'Jacobin' definitions:

Definition of 'Jacobin'

noun

A member of the radical movement that instituted the Reign of Terror during the French Revolution

From: GCIDE

From: GCIDE

Jacobin \Jac"o*bin\ (j[a^]k"[-o]*b[i^]n), n. [F. See 2d Jack, Jacobite.] [1913 Webster]
1. (Eccl. Hist.) A Dominican friar; -- so named because, before the French Revolution, that order had a convent in the Rue St. Jacques, Paris. [1913 Webster]
2. One of a society of violent agitators in France, during the revolution of 1789, who held secret meetings in the Jacobin convent in the Rue St. Jacques, Paris, and concerted measures to control the proceedings of the National Assembly. Hence: A plotter against an existing government; a turbulent demagogue. [1913 Webster]
3. (Zool.) A fancy pigeon, in which the feathers of the neck form a hood, -- whence the name. The wings and tail are long, and the beak moderately short. [1913 Webster]

From: GCIDE

Blackfriar \Black"fri`ar\, Black friar \Black" fri`ar\(bl[a^]k"fr[imac]`[~e]r). (Eccl.) A friar of the Dominican order, so named because wearing the black mantle of the Dominicans; -- called also predicant and preaching friar; in France, Jacobin. Also, sometimes, a Benedictine.
Syn: Dominican. [1913 Webster]