To desist means to stop doing something, especially when someone in authority tells you to quit. When a teacher says “desist from tapping your pencil,” she's telling you to stop that annoying habit right now. When a police officer orders someone to desist from breaking the law, it's a formal command to stop immediately.

The word carries weight and seriousness. You wouldn't use desist to ask someone to stop humming a tune. You'd use it when the behavior needs to end because it's causing problems, breaking rules, or bothering others. A principal might order students to desist from running in the halls. A judge might order a company to desist from false advertising.

Desist often appears in legal language, like “cease and desist,” which is a formal order to stop doing something and not start again. When you desist, you don't just pause for a moment. You stop completely and don't go back to that behavior. The word implies that continuing would be wrong, harmful, or against the rules.