Tympanum

n. pl. E. Tympanums (#), L. Tympana (#).

1. (Anat.) One of the naked, inflatable air sacs on the neck of the prairie chicken and other species of grouse.
2. (Arch.) 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.
1. The ear drum, or middle ear. Sometimes applied incorrectly to the tympanic membrane. See Ear.
2. A chamber in the anterior part of the syrinx of birds.
3. The recessed face of a pediment within the frame made by the upper and lower cornices, being usually a triangular space or table.
4. The space within an arch, and above a lintel or a subordinate arch, spanning the opening below the arch.