Cellulite is the dimpled, uneven look that fat just under the skin can give, often on the thighs or bottom. Magazines and ads talk about it as a problem that must be fixed; doctors are usually calmer — many adults have it, and it is not a disease. The word came in from French in the 1960s, so it is newer than it sounds. Though actually, it sits beside a much more serious cousin: cellulitis is an infection, not a look. One is how skin can appear; the other is an illness.