An iconoclast originally referred to a person who destroyed icons, that is, sacred paintings or sculpture. An example is Byzantine emperor Leo III, who ordered the destruction of all icons of Jesus, the Virgin Mary, and the Saints in his empire. For more discussion of historical iconoclasts, see Iconoclasm.
The more common meaning in current usage is that an iconoclast is a person who carries out symbolic or quixotic acts of protest against Authority figures, the connotation being that the iconoclast opposes the imposition of authority itself rather than any particular policy or action.
The term may also refer to a person who reacts against popular culture or ideals.