Definitions for "-ist"
A noun suffix denoting an agent, or doer, one who practices, a believer in; as, theorist, one who theorizes; socialist, one who holds to socialism; sensualist, one given to sensuality.
English suffix denoting a person - it describes that person's chief duty, or belief. For example, a socialist is a person who believes in the tenets of socialism; a sexist is a person who believes that one sex or gender is superior to the other; and a receptionist is a person who performs duties in the reception area of an office. Other examples are listed below.