/dät fī(-ə)l/
[UNIX]
n. A file which is not visible to normal directory-browsing tools (on UNIX, files named with a leading dot are, by convention, not normally presented in directory listings). Many programs define one or more dot files in which startup or configuration information may be optionally recorded; a user can customize the program's behavior by creating the appropriate file in the current or home directory.
See also rc file.