Real Dictionary

dentil in American English
any of a series of small rectangular blocks projecting like teeth, as from under a cornice
noun: any of a series of closely spaced, small, rectangular blocks, used esp. in classical architecture beneath the coronas of Ionic, Corinthian, and Composite cornices

dentil in British English
noun: one of a set of small square or rectangular blocks evenly spaced to form an ornamental row, usually under a classical cornice on a building, piece of furniture, etc