Pronunciation: (tim'pu-num),[key] —n., —pl.-nums, -naPronunciation: (-nu).[key] 1. Anat.,Zool. a. See middle ear. b. See tympanic membrane. 2. Archit. a. the recessed, usually triangular space enclosed between the horizontal and sloping cornices of a pediment, often decorated with sculpture.
b. a similar space between an arch and the horizontal head of a door or window below.
3. Elect.the diaphragm of a telephone.
4. a drum or similar instrument.
5. the stretched membrane forming a drumhead.