Two definitions:

1. In reductionistic simplification (which is the kind of simplification that comes more naturally to the stereotypically masculine mind), some of the parts of the whole are kept without change or simplification and others are taken away entirely. For example: In the evolution of katakana, 加 was simplified to 力. The left part of the kanji was kept (at 100% resolution), and the right part was taken away (i.e., put to 0% resolution).
2. In holistic simplification (which is the kind of simplification that comes more naturally to the stereotypically feminine mind), none of the parts of the whole are taken away—well, at least fewer of the parts are taken away. Instead, the whole is taken as a whole, and kept as a whole, with the simplification being a matter of decreasing the resolution in an overall way. For example: In the evolution of hiragana, 守 was simplified to す. With enough imagination, squinting at the former can blur it into the latter. That is, “defocusing” blurs the shape into something of lower detail, and then “refocusing,” with stylization added to the result, brings back something sharply focused and aesthetically good, but now with a more manageable amount of detail.