1. The region of the atmosphere above the troposphere and below the mesosphere.
2. An extremely high or the highest point or degree on a ranked scale: business expenses in the stratosphere.

[French stratosphère : Latin strātus, a spreading out; see stratus + -sphère, sphere (from Old French espere; see sphere).]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.