water vapor

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

• noun Water in a gaseous state, especially when diffused as a vapor in the atmosphere and at a temperature below boiling point.

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

• noun water in a gaseous state, especially when diffused in the atmosphere
• noun steam

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

• noun water in a vaporous form diffused in the atmosphere but below boiling temperature