from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The lowest region of the atmosphere between the earth's surface and the tropopause, characterized by decreasing temperature with increasing altitude.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The lower levels of the atmosphere extending from the earth's surface up to the tropopause. It is characterized by convective air movements and a large vertical temperature change.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the lowest atmospheric layer; from 4 to 11 miles high (depending on latitude)
From French troposphère. (Wiktionary)