smoke screen

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

• noun A mass of dense artificial smoke used to conceal military areas or operations from an enemy.
• noun An action or statement used to conceal actual plans or intentions.

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

• noun Alternative form of smoke screen.

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

• noun (military) screen consisting of a cloud of smoke that obscures movements
• noun an action intended to conceal or confuse or obscure