First, a bit of business: you may not have read our naming policy on the way in. It requires that you use a full, real (sounding) first and last name for your display name. A single name isn't enough. You can change your display name here. Thanks!
As to your question: the word "retrofitted" means that something old has been modified to work according to some new standard. It's not any kind of special computer term, just an ordinary English word. For example, the old classes java.util.Vector and java.util.Hashtable were "retrofitted" to implement the interfaces java.util.List and java.util.Map, respectively; these interfaces were introduced in JDK 1.2, while the original classes have existed since JDK 1.0 .
This term is not very common in Java. The only place it seems to make sense is in the example that Ernest gave. If that doesn't answer your question, please provide some context for where you saw this term used?