not a living soul
Not a single person. Don't worry, I'll make sure he doesn't tell a living soul about what he saw. As we entered the town, there wasn't a living soul on the streets, and the whole place was eerily silent.
not a living soul
Fig. nobody. (See some of the possible variations in the examples.) I won't tell anybody—not a living soul. I won't tell a living soul.
not a living soul
People say not a living soul to mean nobody at all. You must tell no-one. Not a living soul! No, she told herself, he would not have told his suspicions to a living soul.