I'm not sure that explains it right. Go to the source for the best definition of short cycle memory: http://drjones.nerdcamp.net/
Short-cycle memory is a special UI that allows to have memory and many modes without the need to cycle through all of them.
With classic memory you have a few modes, and if you want to go back to the first mode, you have to cycle through the remaining modes.
With no memory, you always start at the 1st mode and don't always have to click through all the modes, but you have no memory.
With short-cycle memory, a mode is memorized (i.e. if the light is switched off an on again, it comes on in that previously used mode), but when you change modes again, it will restart in the first mode instead of the next mode, so you don't have to cycle through all the modes. This combines memory with the advantages of a no-memory-UI. It effectively hides every mode behind all it's predecessors and is very effective if you have your favourite modes in front and blinkies or other rarely used modes at the end. I call it "short-cycle" in contrast to the classic cycle-through-all-modes memory, but it was actually invented by sixty545 at BLF.
It's a great way to avoid hi and blinky modes when those modes are defined at the end of the mode list.