hot air

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

• noun Empty, exaggerated talk.

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

• noun Air that has been heated, especially so as to function as the lifting agent of a hot-air balloon.
• noun Empty, confused or exaggerated talk having no meaning or substance.

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

• noun loud and confused and empty talk
• noun air that has been heated and tends to rise