Pronunciation: (strat'u-sfēr"), [key]
1. the region of the upper atmosphere extending upward from the tropopause to about 30 miles (50 km) above the earth, characterized by little vertical change in temperature.
2. (formerly) all of the earth's atmosphere lying outside the troposphere.
3. any great height or degree, as the highest point of a graded scale.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.