The Jinx is a literal curse which plays a prominent role in The Naming of the Shrew. Apparently any monster can do it, and upon saying "Jinx" after repeating the same phrase as someone in unison, it causes their mouth to vanish indefinitely until someone says their name.
This causes the revelation that Lydia is not the true name of Lydia Dracula, and she eventually gets revenge by jinxing everyone.