Changable graphic appearance and/or interface of software on a GUI. Akin to the car equivilent of a paint or body kit that does not change the car underneath but appears different.
Usually the best skins are created by Internet hobbyists. Some skins are themed as marketing tools for movies, games, TV shows etc. such as a "Terminator 3" skin featuring robots from the movie.
- Winamp, an Audio-Video Software programs, uses skins. Version 2 allows a different appearance but keeps generic button-placement and menuing system. Winamp version 3 and Windows Media Player have skins with a variety of unique and radically different interface changes.