Or, see subject, in terms of themselves

Or, perhaps I should have another whiskey? Yes... that seems more likely!
(THHGTTG)

SEA - self extracting acronym

Sorry, no good. Not recursive.

HELP = Help Explain Linux Please

Windows Is Not DOing What it Should - Xorn Poo!
Windows Is Now DOing What it Shouldn't - Very Irritated Sysadmin Tells All

Leopard easily outstrips popular aardvarks rather dull ... time for bed!

LINUX = Linux Is Normally Using X

SLACKWARE = Slackware Lovers Acquire Computing Knowledge We Are Real Experts

DEBIAN ETCH = Debian Etch Because It Always Naturally Evokes Total Computing Happiness

(not really )

UBUNTU = Ubergeeks Belittle Users New To UBUNTU

Sorry. Not recursive. But I can't think of one for Ubuntu. Too many U's. Good distro, though.
P.S.
UBUNTU = Ubuntu Belittlers Underestimate Non Techie Users

It's creepy because a lot of these fit perfectly.

It wouldn't be nearly as fun if they didn't

Isn't it? It doesn't really make sense when expanded but then neither do most of the acronyms proposed so far.

It's called tail recursion.

Ubuntu's Boring UNTill Used

Here's a way to define an acronym only in terms of itself (i.e completely recursively!) that occured to me the other day.

Take an acronym, eg xkcd (used cos it's utterly meaningless and unpronounceable) and form acronyms containing all its letters, but in different orders, untill you have an acronym where each letter is at the front. You can then define the original acronym, and all the new ones, in terms of each other.

Take xkcd.

Form kcdx, cdxk, dxkc.

Then expand xkcd into "xkcd kcdx cdxk dxkc"

You can then expand kcdx into "kcdx cdxk dxkc xkcd" and so on for each of the others.

Woohoo! Complete abstraction.