Eardrum n. : The tympanum. See Illust. of Ear.

Example:
What causes your Eardrum to make a popping sound as you ride up a tall building in an elevator?

Taxonomy
tympanic membrane, membrane, middle ear, perforation of the eardrum, free encyclopedia, membrana tympani, tympanum, bone, ear ossicles, Inner ear, cone of light, four quadrants, nerves, Anatomy of the human ear, thin membrane, external ear, tympanic cavity, external auditory meatus.

Defination from the web:
eardrum), is a thin membrane that separates the external ear from the middle ear. ... Eardrum (Umbo) • Ossicles (Malleus, Incus & Stapes) • muscles (Stapedius, Tensor tympani) • Eustachian tube (Torus tubarius) Inner ear/Labyrinth ...