Latinization of "with a grain of salt," almost always preceded by "take" (as with the English equivalent), meaning to regard with a degree of skepticism or without being taken literally. All of the jubilation over the new president should, as ever, be taken cum grano salis, as no single person will be able to fix the entire country's problems. Jeff's stories tend to be rather exaggerated, so you should usually take them cum grano salis.