tympanum

noun

1. A triangular space between the sides of a pediment.
2. The space within an arch, and above a lintel or a subordinate arch, spanning the opening below the arch.
3. The middle ear.
4. The eardrum.
5. A hearing organ in frogs, toads and some insects.
6. In certain birds, the labyrinth at the bottom of the windpipe.
7. 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.