sofa bed

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A sofa whose seat unfolds to form a bed.

Century Dictionary and Cyclopedia

1. n. 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.

Wiktionary

1. n. alternative spelling of sofa-bed.

GNU Webster's 1913

1. n. a sofa so contrived that it may be extended to form a bed; -- called also sofa bedstead.

WordNet 3.0

1. n. a sofa that can be converted into a bed