zealot

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One who is zealous, especially excessively so.
2. n. A fanatically committed person.
3. n. A member of a Jewish movement of the first century A.D. that fought against Roman rule in Palestine as incompatible with strict monotheism.

Century Dictionary and Cyclopedia

1. n. One who is zealous or full of zeal; one carried away by excess of zeal; an immoderate partizan: generally in a disparaging sense.
2. n. [capitalized] One of a fanatical sect or party (the Zelotæ) among the Jews of Palestine under Roman dominion, who on account of their excesses in behalf of the Mosaic law were also called Sicarii or Assassins. The Zealots gained the ascendancy in a civil war, and withstood the Romans so fiercely as to bring about the total destruction of Jerusalem, a. d. 70. Zealots are also mentioned (perhaps by confusion) as a sect of the Essenes, similarly characterized by fanatical zeal for their ascetic practices.

Wiktionary

1. n. One who is zealous, one who is full of zeal for his own specific beliefs or objectives, usually in the negative sense of being too passionate; a fanatic
2. n. historical A member of a radical, warlike, ardently patriotic group of Jews in Judea, particularly prominent in the first century, who advocated the violent overthrow of Roman rule and vigorously resisted the efforts of the Romans and their supporters to convert the Jews.
3. n. historical A member of an anti-aristocratic political group in Thessalonica from 1342 until 1350.

GNU Webster's 1913

1. n. One who is zealous; one who engages warmly in any cause, and pursues his object with earnestness and ardor; especially, one who is overzealous, or carried away by his zeal; one absorbed in devotion to anything; an enthusiast; a fanatical partisan.

WordNet 3.0

1. n. a fervent and even militant proponent of something
2. n. a member of an ancient Jewish sect in Judea in the first century who fought to the death against the Romans and who killed or persecuted Jews who collaborated with the Romans