Meteorol.the layer of the upper atmosphere where most atmospheric ozone is concentrated, from about 8 to 30 mi. (12 to 48 km) above the earth, with the maximum ozone concentration occurring at an altitude of about 12 mi. (19 km). Also called o•zo•no•sphere Pronunciation: (ō-zō'nu-sfēr"). [key]
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.