The following comes from Scott Bayless, former Senior Producer at Sega of America...
Sadly I have to take responsibility for that ghastly phrase. Marty Franz [Sega technical director] discovered that you could do this nifty trick with the display system by hooking the scan line interrupt and firing off a DMA at just the right time. The result was that you could effectively jam data onto the graphics chip while the scan line was being drawn – which meant you could drive the DAC's with 8 bits per pixel. Assuming you could get the timing just right you could draw 256 color static images. There were all kinds of subtleties to the timing and the trick didn't work reliably on all iterations of the hardware but you could do it and it was cool as heck.
So during the runup to the western launch of Sega-CD the PR guys interviewed me about what made the platform interesting from a technical standpoint and somewhere in there I mentioned the fact that you could just "blast data into the DAC's" Well they loved the word 'blast' and the next thing I knew Blast Processing was born. Oy.
This 'blast processing' line was one that plagued many a Nintendo fan back in the day. I remember many a classroom argument over the SNES/Genesis, and blast processing always came up. If only I could go back in time with this article!