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.