dot file

dot file [UNIX] n.  A file that is not visible by default 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.  (Therefore, dot
   files tend to {creep} -- with every nontrivial application
   program defining at least one, a user's home directory can be
   filled with scores of dot files, of course without the user's
   really being aware of it.)  See also {profile} (sense 1), {rc
   file}.