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.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.