When someone sets their teeth, it means to clench or grind them together tightly. However, there are several other words and phrases that can be used as synonyms for this action. Some examples include gritting teeth, clamping down, locking jaw, bracing oneself, biting down, grinding molars, and gnashing teeth. Each of these phrases conveys a similar sense of tension and determination, often in response to stress, anger, or pain. By using one of these synonyms instead of the more common phrase "set teeth," writers and speakers can add variety and nuance to their descriptions of character behavior and emotions.