Final answer:
A group of three or more inmates who engage in activity that poses a threat to the safety of other inmates or the prison staff is called a prison gang.
Step-by-step explanation:
A group of three or more inmates who engage in activity that poses a threat to the safety of other inmates or the prison staff is called a prison gang. Prison gangs are organized groups that operate within correctional facilities and typically engage in criminal activities such as violence, drug trafficking, and extortion.