Baptized is both adjective and verb:
v. to be baptized, . "Water got up my node while I was being baptized".
adj. "I am a baptized christian".
Ozzy is correct in that you cannot be unbaptized, without first having been baptized, if you are using the verb. However, if using the adjective it is possible. So, what we need to do is define the adjective use of the word baptized. If Henry is baptized and Jane is unbaptised, then what is the difference, or more importantly, what is the attribute pertaining to Henry, that is missing from Jane. This is where I bring in the church's concept of sacraments and salvation.
Baptism is the most important sacrament displayed. (I'm using the verb baptism). By which Christians obtain salvation through the grace of Christ. Having salvation one is said to be a baptized Christian. The attribute difference between Henry and Jane is baptism, (salvation). (I'm using the adjective baptism).
This goes to demonstrate how the Watchtower society colloquialisms can be used to identify method. It is commonly understood that as an unbaptized publisher, a person is willing to distribute Watchtower material before physically identifying themselves as part of that organization. The Watchtower society only uses the verb baptize. This is important. Once a person identifies themselves physically as a Jehovah's witness, then the control mechanisms kick in. (disfellowshipping and shunning)
The Watchtower society is not interested in the adjective form, salvation is only attainable through them. You leave the organization, you die.