This is probably common knowledge, but I thought I'd offer it as bait because I have a question.

'Icebreakers,' Case said, over the rim of the red mug. 'Ice from _ICE,_ intrusion countermeasures electronics.'
- William Gibson, Neuromancer, Ch. 2

What, if anything, does rez stand for?

“Rez” is a backronym from “de-rez”, which is “deresolution.” It was the euphemism for “killing” programs in the film Tron.