As with a few other New Testament words, "baptise" and "baptism" are given meanings that differ from their plain translations.
In fact, they are used to validate a number of different ceremonies.
But the true translation of these words, and their New Testament examples, show that only one can be valid.
The New Testament Greek noun is baptisma and means "immersion" or "submersion" (Strong's Concordance). The verb is baptizo (pronounced bap-tid-zo) which means "to immerse" or "to submerge".
The English words "baptism" and "baptise" convey another meaning by being anglicised rather than translated.
There are some adults who say they have been "baptised" - as babies. But what most of them experienced was being sprinkled with water in a ceremony that is often called "christening".
This teaching claims regeneration, salvation (and more) for the sprinkled baby as certain words are pronounced over the child.
However, in later years the adult "baptised" person is likely to believe these things to be true.
The New Testament describes two examples of immersion in water that actually took place:
Acts 8'27-39 says: "they came up out of the water" to explain Philip immersing the Ethopian believer.
Matthew 3'13-16 says: "came up immediately from the water" to explain John immersing Jesus.