Tympanum
Pronunciation : Tym"pa*num, n.; pl. E. Tympanums
Part of Speech : L.
Etymology : [L., a kettledrum, a drum or wheel in machines, the triangular area in a pediment, the panel of a door, Gr. Type, and cf. Timbrel.]
Definition : 1. (Anat.) (a) The ear drum, or middle ear. Sometimes applied incorrectly to the tympanic membrane. See Ear. (b) A chamber in the anterior part of the syrinx of birds.
2. (Zo?l.)
Defn: One of the naked, inflatable air sacs on the neck of the prairie chicken and other species of grouse.
3. (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.
4. (Mech.)
Defn: 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.
Tympana.
Source : Webster's Unabridged Dictionary, 1913