Jacobin

1. (n.) A Dominican friar; -- so named because, before the French Revolution, that order had a convent in the Rue St. Jacques, Paris.
2. (n.) One of a society of violent agitators in France, during the revolution of 1789, who held secret meetings in the 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.
3. (n.) 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.
4. (a.) Same as Jacobinic.