zealot

Short definition from Wiktionary

Noun

1. 1
   One who is zealous, one who is full of zeal for their own specific beliefs or objectives, usually in the negative sense of being too passionate; a fanatic.
2. 2
   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. 3
   A member of an anti-aristocratic political group in Thessalonica from 1342 until 1350.
4. 4
   Alternative letter-case form of zealot.