mattress

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

• noun A usually rectangular pad of heavy cloth filled with soft material or an arrangement of coiled springs, used as or on a bed.
• noun An airtight inflatable pad used as or on a bed or as a cushion.
• noun A closely woven mat of brush and poles used to protect an embankment, a dike, or a dam from erosion.

from The Century Dictionary.

• noun A bed consisting of a bag filled with straw, hair, moss, sponge, husks, excelsior, or other soft and elastic material, and usually quilted or tacked with transverse cords at short intervals to prevent the contents from slipping.
• noun In hydraulic engineering, a mat or mass of brushwood, willow rods, light poles, or other like material, roughly woven or tied together and used to form foundations for dikes and jetties, or as aprons, fencing, curtains, or surfacing for dikes, dams, embankments, and similar constructions, either for assisting to hold together loose material or to prevent injury by the erosion of water.

from the GNU version of the Collaborative International Dictionary of English.

• noun A large pad stuffed with hair, moss, or other suitable soft material, and quilted or otherwise fastened, used as or in a bed, to support the human body while lying down.
• noun (Hydraulic Engin.) A mass of interwoven brush, poles, etc., to protect a bank from being worn away by currents or waves.
• noun A variety of mattress{1} having springs inside to provide a flexible support; it is considered more comfortable than a stuffed mattress.

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

• noun A pad on which a person can recline and sleep, usually having an inner section of coiled springs covered with foam or other cushioning material then enclosed with cloth fabric.
• noun A form of retaining wall used to support foundations or an embankment

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

• noun a large thick pad filled with resilient material and often incorporating coiled springs, used as a bed or part of a bed