Tym'pa-nŭm, n.

n. [Lat. tympanum, Gr. τύμπανον, a kettle-drum, a drum or wheel in machines, the triangular area in a pediment, the panel of a door. See TYMPAL.]

1Sense 1. (Anal.) (a.) The middle hollow portion of the ear containing the small bones, and separated by a membrane from the external passage; also, this membrane itself, on which atmospheric vibrations act directly in producing sound; — often called the drum of the ear. (b.) In birds and reptiles, the flat scale or membrane which forms the external organ of hearing.

2Sense 2. (Arch.) (a.) The naked face of a pediment, being usually a triangular space or table in the corners or sides of an arch, often enriched with figures. (b.) The die of a pedestal. (c.) The panel of a door. Gwilt.

3Sense 3. (Mech.) A drum-shaped wheel with spirally curved partitions by which water is raised to the axis, when the wheel revolves with the lower part of the circumference submerged; — used for raising water, as for irrigation.