Meme combining is the special brand of shooping used to revive an older meme or image with another meme, image or even concept, thus bringing meme faggotry to a whole new level. This is usually seen in shoops where part of an older image has been replaced with part of a newer one, producing mixed reactions that may spark new lulz. The Cancer That Is Killing /b/ can only learn how to use exploitables to achieve a similar result because they don't have the required vision necessary to create it.
tl;dr do this only if you're certain of the results.
Placing two memes together and waiting for results.
Methodology
Most of the time, Meme Combining is achieved successfully when you shoop someone's head on to another. However, this by no means implies the results will always be satisfactory. A truly lulzy shoop invokes both memes to the fullest.