sleeping bag

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

• noun A large, insulated, usually zippered bag for sleeping, especially outdoors.

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

• noun A padded or insulated bag large enough to surround the whole body and which keeps the user warm while sleeping, used as a substitute for bedclothes.

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

• noun large padded bag designed to be slept in outdoors; usually rolls up like a bedroll