1. The immersion or dipping of a believer into water, symbolizing the complete renewal and change in the person's life and testifying to the death, burial, and resurrection of Jesus Christ as the way to salvation: "At some point, close to the time of Jesus, Judaism placed a heavy emphasis on ritual washings to cleanse from impurity. Jews started baptizing Gentile converts, although circumcision still remained the primary entrance rite into Judaism."

"Baptism is not just to cleanse the body, but as an outward sign of an inward spiritual cleansing and commitment. Baptism is a sign of repentance, as practiced by John the Baptist, and of faith in Jesus Christ, as practiced by Jesus’ disciples."

2. A ceremonial immersion in water, or application of water, as an initiatory rite or sacrament of the Christian church: "Baptism is not just to cleanse the body, but as an outward sign of an inward spiritual cleansing and commitment. Baptism is a sign of repentance, as practiced by John the Baptist, and of faith in Jesus Christ, as practiced by Jesus’ disciples.
3. A trying or purifying experience or initiation: "Zelda went through a baptism on her first day of work."

Self baptism: "Back in 1606 there was a Christian congregation in England that was pastored by John Smyth. In 1608 this church emigrated to Amsterdam because of religious persecution in England."

"While in Amsterdam, Smyth became convinced that the scriptures require believers' baptism, not infant baptism. Since Smyth had not been baptized in the way he felt was correct, he baptized himself, then baptized the other members of the church he was leading."