The modern-day definition of zealot is "a fervent or militant proponent of something." The original Zealots, or Zelotes, from the Greek word pronounced dzay-low-tace, were members of a Jewish sect that at first just refused to pay tribute (see Custom and Tribute) to the pagan Romans who then occupied the land of Israel (see Ancient Empires - Rome), declaring that God was their only King. This eventually however escalated to violence and assassination against the Romans, and anyone else, including other Jews, who cooperated with the Romans. The overwhelming power of the Roman military caused their rebellion to fail, after which they became scattered rebels who were also known as Sicarii ("dagger men"), from their deadly use of the sica, a Roman dagger. The Zealots were leading members of the revolt against Rome in 66-70 AD (see Fall of Jerusalem In 70 A.D.), and at Masada they committed suicide rather than surrender to the Roman Tenth Legion (see Roman Legions). At least one of The Twelve Apostles, who were personally chosen by Jesus Christ, after being directed by God in prayer, was a Zealot - Simon (not to be confused with the other Simon who is known as Peter, although Peter's temperment in his earlier years well-suited him to have been a Zealot).
At Least One Zealot Among The Chosen Apostles
"In these days He went out to the mountain to pray; and all night He continued in prayer to God. And when it was day, He called His disciples, and chose from them twelve, whom He named apostles [see Disciples and Apostles]; Simon, whom He named Peter, and Andrew his brother, and James and John [see also Aunt Mary?], and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Simon who was called the Zealot, and Judas the son of James, and Judas Iscariot, who became a traitor." (Luke 6:12-16 RSV)
"And when He had said this, as they were looking on, He was lifted up, and a cloud took Him out of their sight. And while they were gazing into heaven as He went, behold, two men stood by them in white robes, and said, "Men of Galilee, why do you stand looking into heaven? This Jesus, who was taken up from you into heaven, will come in the same way as you saw him go into heaven." [see The Return Of Jesus Christ]. Then they returned to Jerusalem from the mount called Olivet [i.e. The Mount Of Olives], which is near Jerusalem, a Sabbath day's journey away; and when they had entered, they went up to the upper room, where they were staying, Peter and John and James and Andrew, Philip and Thomas, Bartholomew and Matthew, James the son of Alphaeus and Simon the Zealot and Judas the son of James. All these with one accord devoted themselves to prayer, together with the women and Mary the mother of Jesus, and with His brothers." [see Mary's Other Children?] (Acts 1:9-14 RSV)
Fact Finder: Should Christians be "zealous" ("eager") in their faith and obedience to God?
See also Christian Living