Putrid means rotten and foul-smelling, the way food gets when it decays. When meat sits out too long, it becomes putrid: the smell makes you wrinkle your nose and turn away immediately. A forgotten sandwich at the back of a locker, a spoiled carton of milk, or garbage left in the sun for days: these things turn putrid as bacteria break them down.

It describes that unmistakable stench of decay. You know something is putrid before you even see it, because the smell hits you first. A putrid odor is so strong and unpleasant that your body reacts instinctively, warning you to stay away from something that could make you sick.

People sometimes use putrid more broadly to describe anything disgusting or terrible. You might hear someone call a movie “putrid” if they think it's absolutely awful, though that exaggerates the word's literal meaning. But when something truly smells putrid (like a dumpster on a hot day or food that's gone bad), there's no better word to capture that revolting, stay-far-away kind of stench.