The term "up setter" can refer to a person or thing that causes disruption, upheaval, or annoyance. There are a variety of synonyms that can be used to describe such a person or thing, including agitator, disrupter, troublemaker, instigator, provoker, irritant, and nuisance. An agitator is someone who intentionally stirs up trouble or discontent. A disrupter causes disturbance or interruption of normalcy. A troublemaker is someone who causes problems or creates difficulties. An instigator incites others to take action or behave in a particular way. A provoker is someone who intentionally incites aggression or hostility. An irritant is something that causes annoyance or discomfort. A nuisance is something or someone that causes inconvenience or irritation.