ozone layer

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

• noun A region of the atmosphere lying mostly in the stratosphere, between about 15 and 30 kilometers (10 and 20 miles) in altitude, containing a relatively high concentration of ozone that absorbs solar ultraviolet radiation in a wavelength range not screened by other atmospheric components.

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

• noun A region of the stratosphere, between 15 and 30 kilometres in altitude, containing a relatively high concentration of ozone; it absorbs most solar ultraviolet radiation

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

• noun a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun