iconoclast

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One who attacks and seeks to overthrow traditional or popular ideas or institutions.
2. n. One who destroys sacred religious images.

Century Dictionary and Cyclopedia

1. n. A breaker or destroyer of images; a person conspicuously hostile to the use of images in Christian worship. Specifically — [capitalized] One of a sect or party in the Eastern Empire in the eighth and ninth centuries which opposed all use and honor or worship of icons or images, and destroyed them when in power. The party of Iconoclasts was originated by the emperor Leo the Isaurian, and afterward continued or revived by Constantine Copronymus and other emperors, especially Leo the Armenian and Theophilus. The emperors named treated those who honored icons with great cruelty, and after the death of the last of them the party of Iconoclasts soon became extinct. See iconoclastic.
2. n. One of those Protestants of the Netherlands who, during the reign of Philip II., riotously destroyed the images in many of the Roman Catholic churches.
3. n. Hence Any destroyer, denouncer, or exposer of errors or impostures; one who systematically attacks cherished beliefs.

Wiktionary

1. n. One who destroys religious images or icons, especially an opponent of the Orthodox Church in the 8th and 9th centuries, or a Puritan during the European Reformation.
2. n. One who opposes orthodoxy and religion; one who adheres to the doctrine of iconoclasm.
3. n. One who attacks cherished beliefs.

GNU Webster's 1913

1. n. A breaker or destroyer of images or idols; a determined enemy of idol worship.
2. n. One who exposes or destroys impositions or shams; one who attacks cherished beliefs; a radical.

WordNet 3.0

1. n. a destroyer of images used in religious worship
2. n. someone who attacks cherished ideas or traditional institutions