a zealot: a person whose commitment to some cause, law, or way of life is total and openly shown
The picture behind this word is heat. It belongs to the family of ζῆλος, the boiling ardor that can either warm or scald, and it names the person in whom that heat burns. Someone called this is not merely interested in a cause: that person has taken its side and will defend it.
Greek usually tells you straight away what the heat is aimed at, because the word almost always comes attached to the thing the person burns for. That attachment is what ties these uses together and what tells them apart:
- devotion to God himself and to the law he gave (Acts 21:20; Acts 22:3)
- devotion to the traditions handed down from the fathers (Galatians 1:14)
- eagerness for spiritual gifts, for what is good, and for good works (1 Corinthians 14:12; 1 Peter 3:13; Titus 2:14)
Paul uses the word of his younger self, and he does not mean it as a confession of a bad attitude. He means his devotion was total and public, standing in the honored line of Israel's zealous heroes such as Phinehas and Elijah. Yet that same total devotion is what drove him to hunt down the church, which is why he can describe it without embarrassment and still count his old life a loss.
Two verses use the word as a name rather than a description: one of the twelve apostles is simply called "Simon the Zealot" (Luke 6:15; Acts 1:13). Whether that nickname marked him as part of an armed resistance movement, or only described a man known for fierce loyalty to the law, is one of the genuinely open questions about the twelve.
Nuances
What the nickname "the Zealot" identifies about the apostle Simon in Luke 6:15 and Acts 1:13: membership in an organized revolutionary movement, or a personal reputation for religious zeal.
- majorityThe epithet marks personal religious zeal for the law, in the tradition of Phinehas, since an organized party called the Zealots is not attested before the revolt of 66 CE.; Morton Smith, "Zealots and Sicarii, Their Origins and Relations," Harvard Theological Review 64 (1971): 1-19; Richard A. Horsley, "The Zealots: Their Origin, Relationships and Importance in the Jewish Revolt," Novum Testamentum 28 (1986): 159-192; David M. Rhoads, Israel in Revolution: 6-74 C.E.: A Political History Based on the Writings of Josephus (Philadelphia: Fortress, 1976)
- minorityThe epithet places Simon within a continuous militant freedom movement reaching back to Judas the Galilean, so the label already carried a political and revolutionary sense in his lifetime.; Martin Hengel, The Zealots: Investigations into the Jewish Freedom Movement in the Period from Herod I until 70 A.D., trans. David Smith (Edinburgh: T&T Clark, 1989)