Mine is OOO for Out Of Office. I always misread it in my head like a ghost and it takes me a few seconds to process. It also doesn't translate to speech—you have to say the whole thing.
Interested to see if others have similar acronyms they beef with.
Then there's the less talked about sibling, WYSIWYM (What You See Is What You Mean). These attempt to reduce bloat in output by being more abstract in what they manipulate instead of promising pixel-perfect results.
It's in contrast to something like LaTex or markdown, where you edit the syntax for formatting directly and don't see the final result until you preview or save it.