Anasazi symbols are symbols that originated from the Anasazi people, one of the native American tribes who settled around the southwestern United States of America. They are used as protections against wendigos.
Background
Dean drew these symbols during their encounter with a wendigo, based on the notes written by John in his journal. According to John's notes, a wendigo could not cross over anasazi symbols.
An anasazi symbol drawn on the ground.
Dean drew several of these symbols around their campsite, implying that drawing a lone symbol would not stop a wendigo, and that several of the symbols must be used together in order to enclose an area safe from the monster, not unlike how one would create a ring of salt or goofer dust. As Dean created the symbols simply by sketching them on the ground, anasazi symbols appeared effective regardless of how they were drawn.