What does "tympanum" mean?

Tympanum: (Zoöl.) One of the naked, inflatable air sacs on the neck of the prairie chicken and other species of grouse.

Additional senses

  1. 2.(Arch.) (a) The recessed face of a pediment within the frame made by the upper and lower cornices, being usually a triangular space or table. (b) The space within an arch, and above a lintel or a subordinate arch, spanning the opening below the arch.
  2. 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.

Sources