"For whosoever will save his life will lose it; but whosoever shall lose his life for my sake and the gospel's the same shall find it" (Mark 8:35 KJV).
A martyr, as revealed by the word of God, is one who is persecuted for what he believes and is killed by his oppressors because he refuses to denounce what he believes (Acts 12:2; Revelation 2:13, 6:9, 20:4).
In Acts 6:8-15, Acts 7:1-60, and Acts 22:20, we read of the martyrdom of Stephen, a godly man who single-handedly stood up against the haters of the good news and didn't back down. Those wicked people really hated him because of his stand for the truth, so they arrested him and had him stand before a mock court, only to attack and kill him afterward because he wasn't intimidated by them. The closing statement of his life was, "Lord Jesus, receive my spirit," (KJV). So this gentle, peaceful man died a martyr, and he didn't deserve this violent death, yet he gave his life so that Jesus could be glorified.
John the Baptist was also a martyr. His crime was telling Herod, "it is not lawful for thee to have her," (Matthew 14:4 KJV). John the Baptist refused to back down, and as a result, he was thrown into jail by the wicked Herodias, and that cost him his head—literally.
More martyrdom can be found in Hebrew 11:36-40 where we can read of the faithful being tortured, enduring mock trials, being cut asunder, etc. etc. The motives of the martyr can be seen in the closing words of verse 35, "Not accepting deliverance; that they might obtain a better resurrection," (KJV).
These people knew that what they stood for wasn't popular and would probably get them killed at some point, however they considered the promises of God better than anything in life.
The Apostle Paul was also a martyr for he said in Acts 21:10-14, "I'm not only willing to go to Jerusalem and be arrested, but also willing to die for the Lord Jesus."
I find it interesting that Paul is only speaking of the death of himself. We read nothing about Paul planning to cause the deaths of others, and then claim martyrdom. In 2 Timothy 4:6-8, Paul continues to inform men of his death, "For I'm now ready to be offered, the time of my departure is at hand," (KJV). Notice that he didn't say, "my departure and the departure of those who want to kill me."
He said that he alone would die at the hands of those who hate the gospel of Jesus Christ. So the interesting thing we learn about martyrdom is, the person dies himself, and he doesn't plan or seek to cause the death of others, whether they be his oppressors or just innocent people.
Let me repeat this just in case someone didn't quite understand—a martyr is someone who is suffering based on what he has believes and is finally killed because of that belief. The martyr dies alone, not plotting the death of others. A martyr is a righteous person in good favor with God, and isn't a fanatic or homicidal. You won't see him walking into a crowded mall and murdering shoppers when his backpack explodes.
So what about these people who explode bombs in shopping centers, airports, trains, etc.? Some said they died as martyrs. But is that really true? I say no. I say such is no different than a fired employee who goes back to the job from which he was dismissed and shoots former bosses and coworkers and then turns the gun on himself when the police close in. Did that person die a martyr? Did the local news media address the shooter as a martyr? Of course not and rightly so, because the news media said such actions are homicides. Those people we hear about on the news who have been blowing up buses, planes, and other crowed areas are cold blooded killers.
They aren't martyrs because the word of God doesn't teach for the faithful to kill people who refuse to accept the Lord. When it concerns acceptance of God, Jesus leaves it up to each person to decide for himself (Matt 11:28-30). Wanting to murder people because they don't accept your belief is not martyrdom, but it is the spirit of the Devil. Consider what Jesus had to say to James and John after they became angry at the villagers who refused to show hospitality to Christ. These men asked Christ for his permission to command fire from heaven to burn up the villagers! Jesus responded by saying, "You know no what manner of spirit ye are of; for the Son of man is not come to destroy men's lives, but to save them," (Luke 9:51-56 KJV). Jesus is interested in people living and not dying, for even when people have rejected his message, he sends the sun and rain on the just and unjust (Matt. 5:45). Jesus gave no command for his followers to strap on bombs and blow up or behead the "infidels!" (Al-Qaeda). Only Satan would deceive men into committing such murderous acts in the name of God (John 8:44).
Rather than kill unbelieving people, Jesus said, "Let both grow together until the harvest," (Mark 13:30 KJV).