pediment

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A wide, low-pitched gable surmounting the façade of a building in the Grecian style.
2. n. A triangular element, similar to or derivative of a Grecian pediment, used widely in architecture and decoration.
3. n. Geology A broad, gently sloping rock surface at the base of a steeper slope, often covered with alluvium, formed primarily by erosion.

Century Dictionary and Cyclopedia

1. n. In architecture, a low triangular part resembling a gable, crowning the fronts of buildings in the Greek styles, especially over porticos. It is surrounded by a cornice, and its flat recessed field or tympanum is often ornamented with sculptures in relief or in the round. Among such sculptures are found the finest remains of Greek art—the pediment-figures of the Parthenon, by Phidias. In the debased Roman and Renaissance styles the same name is given to gables similarly placed, even though not triangular in form, but semicircular, elliptical, or interrupted, and also to small finishing members of any of these shapes over doors or windows. In the architecture of the middle ages small gables and triangular decorations over openings, niches, etc., are often called pediments. These generally have the angle at the apex much more acute than the corresponding gable or gablet in Roman architecture, which, on its part, is markedly higher in proportion, or less obtuse-angled at the summit, than Hellenic pediments. See also cuts under acroterium, octastyle, and pedimented.
2. n. Hence In decorative art, any member of similar outline, forming a triangular or segmental ornament rising above a horizontal band, as in ironwork; such a member above the opening of a screen or the like: it may be entirely open and consist of light scrollwork only.

Wiktionary

1. n. architecture A classical architectural element consisting of a triangular section or gable found above the horizontal superstructure (entablature) which lies immediately upon the columns; fronton

GNU Webster's 1913

1. n. (Arch.) Originally, in classical architecture, the triangular space forming the gable of a simple roof; hence, a similar form used as a decoration over porticoes, doors, windows, etc.; also, a rounded or broken frontal having a similar position and use. See temple.

WordNet 3.0

1. n. a triangular gable between a horizontal entablature and a sloping roof