"Quine," from The Jargon File, version 4.4.7:

quine /kwi:n/ [from the name of the logician
Willard V. Quine, via Douglas Hofstadter]

n. A program that generates a copy of its own source text as its complete output. Devising the shortest possible quine in some given programming language is a common hackish amusement."

One not too obfuscated Perl quine (of several):

$_=q{$_=q{Q};s/Q/$_/;print};s/Q/$_/;print

There is, of course, the definitive quine page.