The term "rotten smell" can be quite unpleasant. Luckily, there are several synonyms you can use to describe this foul odor. One common term is "putrid smell," which refers to something that's decayed and produces a noxious odor. Another synonym is "foul smell," which describes a strong and unpleasant smell. "Stinky" is a more colloquial term and depicts a smell that's particularly offensive to one's sense of smell. "Rancid" smell refers to something that's gone bad due to spoiled food or other organic matter. Other synonyms for a rotten smell include "stench," "fetid," "offensive," and "malodorous." No matter the term used, these words all depict an unpleasant odor.