sofa bed

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

• noun A sofa whose seat unfolds to form a bed.

from The Century Dictionary.

• noun A piece of furniture forming a sofa, as during the day, but capable of being opened or altered in shape so as to furnish a bed at night.

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

• noun Alternative spelling of sofa-bed.

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

• noun a sofa that can be converted into a bed