middle ear

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The space between the eardrum and the inner ear that contains the three auditory ossicles, which convey vibrations through the oval window to the cochlea.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy The cavity in the temporal bone between the eardrum and the inner ear that contains the ossicles, and which conveys sound to the cochlea.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the main cavity of the ear; between the eardrum and the inner ear