The piercings do not have an individual meaning, except perhaps to the individuals with them. However, the meanings are not universal. Piercings are very personal and are not usually made with a specific purpose in mind. Rather, they are a kind of gestalt of the feeling they want to convey first to themselves about themselves and secondarily to observers. I.e., piercings are for the self primarily.
They do convey meaning to observers, but that meaning is more diffuse. It is about the personality of the pierced person. It is about their aesthetic. It is about how they want to be seen, given their own feelings about how they look and what they aspire to look like. They do not necessarily take into account what others will think, nor do they feel responsible for helping others interpret their body decorations. As with hair color and clothing and tattoos, these decorations are somewhat ambiguous in terms of specific meanings. They are meant to be taken as an overall expression of personality, although there is no exact table of what the individual elements of the presentation mean.
So sue me. I did some research and I found an interesting article that gets at this issue, although does not answer is directly. In BODY PIERCING: DOES IT MODIFY SELF-CONSTRUCTION? A RESEARCH WITH REPERTORY GRID, by Cipolletta, et al, the authors find that piercing is primarily a mechanism for self expression. They point out that piercings used to be associated only with the more fringe elements of society—bikers, sailors, criminals and the like. Since the ‘80s, piercings have entered the mainstream, and now, they argue, piercings are a form of expression that is used to help folks feel better about themselves. Along the way in the article, they point out that people with low self esteem or who are in the lower socio-economic classes are more likely to have multiple piercings. This makes sense when you think that people use piercings to help them feel better.
I have quoted a bit from their conclusion, which I think explains things a bit better than I can:
We can, therefore, conclude that piercing represents for the Piercing Tribe’s members much more than a simple body ornament. Piercing the body doesn’t have the same meaning as putting a dress on, but it implies something more: pierced people want to communicate in a radical way, and they do it using their own bodies as a means of communication, which is pierced and marked. The choice of this extreme mode of communication, which goes through the skin, seems to be compatible with the message they want to transmit, that is their own authentic way of being and feeling. Moreover, Charmet and Marcazzan (2000) add: “Body communication is extreme and primitive, for this reason it is suitable to express one’s most genuine parts, prior to intellectual processing and reasoning. If we leave aside the oral one, this is the most effective way to communicate in a determined, mature and conscious manner” (p.84).
The perforation of the body’s, thus, implies a deep inner pursuit. And the pierced body, clearly visible and perceivable, is an authentic and concrete expression of “who you are” and “who you want to be”. It’s an experience with autoplastic purposes, a kind of self-message made in public, a private dialogue spoken aloud. “It derives from the desire to explore the blind area between the mental and the physical sphere in order to pursue an hidden expressive freedom you have got to recover and it is expressive of an inner search which you want to communicate by setting free a creative part of yourself to express a part of your own essence” (Martinelli, 1997, p.7).