A file with a name starting with a dot. These files are hidden from a normal ls (try ls -a instead). Dot files in your home directory are typically configuration files. The other common dot files are ``.'' and ``..'' which exist in every directory, meaning the current directory and the parent directory.
A UNIX file that configures some aspect of the Desktop, related programs, or your computer environment. Dot files are so called because their filenames start with a period or ``dot.'' They are usually created automatically and reside in each user's home directory. You can choose whether or not you want to display dot files in a directory window.
In Linux, files which are to be hidden have filenames beginning with a dot ('.').