It simply means to immerse oneself in something either gas, liquid, or spirit 1 Cor 10:1-4 = Moreover, brethren, I would not that ye should be ignorant, how that all our fathers [the prophets] were under the cloud, and all passed through the sea; And were all baptized unto Moses in the cloud and in the sea; And did all eat the same spiritual meat; And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ. | Many Christians believe in water baptism as a practice which still is beneficial now, and some even declare it as a necessary component of salvation. However we should realize as the above and below verses mention, not all baptism involves water. In fact "baptism" as well as "drink" are used figuratively as well as literally throughout the word of God. |

Mark 1:1-11 = The beginning of the gospel of Jesus Christ, the Son of God; As it is written in the prophets, Behold, I send my messenger before thy face, which shall prepare thy way before thee. The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight. John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins. And there went out unto him all the land of Judaea, and they of Jerusalem, and were all baptized of him in the river of Jordan, confessing their sins. And John was clothed with camel's hair, and with a girdle of a skin about his loins; and he did eat locusts and wild honey; And preached, saying, There cometh one mightier than I after me, the latchet of whose shoes I am not worthy to stoop down and unloose. I indeed have baptized you with water: but he shall baptize you with the Holy Ghost. And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan. And straightway coming up out of the water, he saw the heavens opened, and the Spirit like a dove descending upon him: And there came a voice from heaven, saying, Thou art my beloved Son, in whom I am well pleased. | Luke 3:3 = And he came into all the country about Jordan, preaching the baptism of repentance for the remission of sins; | 

Matt 3:11 = I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire: | Notice that this above verse does not say "he shall baptize you with water, the Holy Ghost, and with fire, but instead with the latter two only - Holy Ghost, and with fire (symbolic). The reason it says it this way is because that's the way it is to be. The water baptism was carried out as a prior symbol of the death, and resurrection of Christ. The new spiritual baptismal event comes to pass on the day of Pentecost. |

Acts 10:37-38 = That word, I say, ye know, which was published throughout all Judaea, and began from Galilee, after the baptism which John preached; How God anointed Jesus of Nazareth with the Holy Ghost and with power: who went about doing good, and healing all that were oppressed of the devil [those who needed deliverance from their afflictions]; for God was with him. | Rom 6:3-4 = Know ye not, that so many of us as were baptized into Jesus Christ were baptized [immersed] into his death? Therefore we are buried with him by baptism [immersion into the spirit of him - not into water] into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. | Col 2:12 = Buried with him in baptism [immersion into his death], wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead. | When we were buried with him, we became spiritually dead to sin the moment we believed unto him. |

John 1:33-34 = And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost. And I saw, and bare record that this is the Son of God. | Acts 1:5 = For John truly baptized with water; but ye shall be baptized with the Holy Ghost not many days hence. | Acts 19:4-5 = Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus. When they heard this, they were baptized in the name of the Lord Jesus. | It does not say water is involved, but they were to be baptized (immersed) in the name of Lord Jesus. | This means that they could now worship God by the spirit [by speaking in tongues, which is perfect communication between them and God - because they did not understand the language they spoke (but God understood it for he gave it to them to worship him by)]. | Acts 10:44-48 = While Peter yet spake these words, the Holy Ghost fell on all them which heard the word. And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost. For they heard them speak with tongues, and magnify God. Then answered Peter, Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we? And he commanded them to be baptized in the name of the Lord. Then prayed they him to tarry certain days. | Verse 47 above throws us a curve.

However we mustn't overlook below at the verses which partially reflects what was before stated, with some expansion of the text - "Then remembered I the word of the Lord". | Acts 11:15-18 = And as I began to speak, the Holy Ghost fell on them, as on us at the beginning. Then remembered I the word of the Lord, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost. Forasmuch then as God gave them the like gift as he did unto us, who believed on the Lord Jesus Christ; what was I, that I could withstand God? When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life. | Peter still was hanging on to Johns baptism when he said "Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we?", and not remembering the Lords promise concerning baptism. However before the Gentiles were baptized, he remembered that Johns baptism was by water as a symbol of the one to come [Jesus] who will baptize with holy spirit. So therefore he commanded the Gentiles to be baptized not in water [as tradition teaches us], but in spirit as the scriptures intended to mean. |

1 Pet 3:21 = The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ: | The "putting away of the filth of the flesh" does not refer to water baptism, but instead the putting off of sin, by our burying it with Christ. However the importance of spiritual baptism is not this, but rather by putting our heart toward God by believing in the resurrection of Jesus Christ as being from God. The below verse speak of the two different usage's of baptism, during transition phase. |

Act 8:35-39 KJV - Then Philip opened his mouth, and began at the same scripture, and preached unto him Jesus. And as they went on [their] way, they came unto a certain water: and the eunuch said, See, [here is] water; what doth hinder me to be baptized? And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God. And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him. And when they were come up out of the water, the Spirit of the Lord caught away Philip, that the eunuch saw him no more: and he went on his way rejoicing. | This passage is one of the primary few used to promote water baptism in the modern Christian church. The truth key is in the context. The eunuch clearly only knew of Johns baptism, as scripture states. Therefore Philip simply honored the ignorant fact, while giving him both baptisms (water, holy ghost), without any explanation needed. The eunuch now saved (by his simple confession), would eventually learn the truth, as the witness was being spread. Which explains why the Lord took Philip away after baptism event, just as the Lord sent him to do the good work.

Conclusion: Baptism, by biblical definition (not secular dictionaries), doesn't always imply water. Plus scripture is figurative, as well as literal. Were it only the latter, then much of Gods word would be illogical, not to mention impossible in the physical sense. The bible is largely a spiritual, not material book. Tip: The key is rightly dividing scripture, not just surface reading it .