UDF

1. Short for Universal Data Format, UDF is a file system developed by Optical Storage Technology Association and is commonly used with CD and DVD drives. UDF is supported on all operating systems, which allows a CD created on a Windows machine to be readable on a Macintosh machine. 
2. Short for User-Defined Function, UDF is a function that can be modified to fit the user's needs.
3. Short for User-Defined Font, UDF is a font specified by the user and not the software program.

Also see: File system, Font, Function