Tympanum /(?)/

pl. Tympanums, Tympana

1. The ear drum, or middle ear. Sometimes applied incorrectly to the tympanic membrane. See Ear. (Anat.)
2. One of the naked, inflatable air sacs on the neck of the prairie chicken and other species of grouse. (Zool.)
3. The recessed face of a pediment within the frame made by the upper and lower cornices, being usually a triangular space or table. (Arch.)
4. 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. (Mech.)