I think if you look at it on a more general sense. Discrete would mean individual in electronic sort of sense. I was talking to a few people the other day comparing the likes of modern desktop computers versus embedded devices like smartphones, tablets, etc. You have all these SoC, PoP which are packing more stuff on a single die (or a chip in a more layman's sense). Then you get discrete ones which a few or only one component sitting in a single die, and are separate from another. That is a CPU would not have just L1/L2/L3 RAM, with embedded devices you get video chip, maybe a radio (for wireless communication) and other things all on one chip.
So basically, I guess discrete switch would be none other than what kolonelkadat describes. In other words individually packed switch.