1. anatomy see middle ear.
2. see eardrum.
3. zoology A membranous external auditory structure, as in certain insects.
4. architecture the ornamental recessed space or panel enclosed by the cornices of a triangular pediment.
5. architecture A similar space between an arch and the lintel of a portal or window.
6. the diaphragm of a telephone.

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. 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.
2. the ear drum, or middle ear. sometimes applied incorrectly to the tympanic membrane. see ear.
3. A chamber in the anterior part of the syrinx of birds.
4. one of the naked, inflatable air sacs on the neck of the prairie chicken and other species of grouse.
5.
6. the recessed face of a pediment within the frame made by the upper and lower cornices, being usually a triangular space or table.
7. the space within an arch, and above a lintel or a subordinate arch, spanning the opening below the arch.
8. 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. an ancient tambourine or hand-drum, either with a single head like the modern tambourine, or with both front and back covered (the back sometimes swelled out as in a kettledrum), and beaten either with the hand or with a stick.
2. in anatomy and zoology: the ear-drum considered as to its walls, its cavity, and its contents.
3. the tympanic membrane; the ear-drum, in the restricted sense of that term: so used in physiology and aural surgery, and in common speech: as, a rupture of the tympanum. see tympanic membrane, under tympanic.
4. in ornithology: the labyrinth at the bottom of the windpipe of sundry birds, as the mergansers and various sea-ducks: a large irregular bony or gristly dilatation of the lower part of the trachea, often involving also more or less of the upper ends of the bronchi. it is chiefly found, or most developed, in the male sex.
5. the naked inflatable air-sac on each side of the neck of certain birds, as grouse, especially the sage-grouse and prairie-hen, in which the ordinary cervical air-cells of birds are inordinately developed and susceptible of great distention. see cut under Cupidonia.
6. in entomology, a tympanic membrane, stretched upon a chitinized ring, one surface being directed to the exterior, the other to the interior, in relation with a tracheal vesicle and with nervous ganglia and nervous end-organs in the form of clavate rods, as in the orthoptera, where such an arrangement constitutes an auditory organ.
7. in architecture: the triangular space forming the field or back of a pediment, and included between the cornices of the inclined sides and the horizontal cornice; also, any space similarly marked off or bounded, as above a window, or between the lintel of a door and an arch above it. the tympanum often constitutes a field for sculpture in relief or in the round. see also cuts under pediment and pedimented.
8. the die or drum of a pedestal. see cuts under dado and pedestal.
9. the panel of a door.
10. in hydraul, engin., a water-raising current-wheel, originally made in the form of a drum, whence the name.
11. A kind of hollow tread-wheel wherein two or more persons walk in order to turn it, and thus give motion to a machine.
12. in botany, a membranous substance stretched across the theca. of a moss.

1. the membrane in the ear that vibrates to sound
2. the main cavity of the ear; between the eardrum and the inner ear
3. a large hemispherical brass or copper percussion instrument with a drumhead that can be tuned by adjusting the tension on it