Here, have a look:
The above link probably explains it better than I can, but it's Sony's patented dithering process to go from 24 or 20 bits down to the 16/44.1 redbook CD standard. Their goal is to capture more than 16 bits of sound in the 16-bit format. They claim that it makes a 16 bit CD sound more like 20 bits of information. Many of the Columbia/Legacy reissues use the SBM process and I think most sound quite good.
Super Bit Mapping is Sony's patented noise shaping process, which can be used w/wo redithering. It reshapes the noise spectrum,including the roundoff noise spectrum associated with bit length reduction, so that instead of having a flat amplitude spectrum at all frequencies, the noise amplitude is lowered across most of the audio band and correspondingly raised at high frequencies, where it is supposedly less audible.