bolster

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

• noun A long narrow pillow or cushion.
• transitive verb To support or prop up with or as if with a long narrow pillow or cushion.
• transitive verb To buoy up or hearten.

from The Century Dictionary.

• To support with a bolster.
• To prop; support; uphold; maintain: generally implying support of a weak, falling, or unworthy cause or object, or support based on insufficient grounds: now usually with up: as, to bolster up his pretensions with lies.
• To furnish with a bolster in dress; pad; stuff out with padding.
• noun Something on which to rest the head while reclining; specifically, a long cylindrical cushion stuffed with feathers, hair, straw, or other materials, and generally laid under the pillows.
• noun Something resembling a bolster in form or use.
• noun A pad or quilt used to prevent pressure, support any part of the body, or make a bandage sit easy upon a wounded part; a compress.
• noun A cushioned or padded part of a saddle.
• noun Naut., pl., pieces of soft wood covered with tarred canvas, placed under the eyes of the rigging to prevent chafing from the sharp edge of the trestletrees.
• noun A part of a bridge intervening between the truss and the masonry.
• noun In cutlery, the part of such instruments and tools as knives, chisels, etc., which adjoins the end of the handle; also, a metallic plate on the end of a pocket-knife handle.
• noun In gunnery, a block of wood on the carriage of a siege-gun, upon which the breech of the gun rests when it is moved.
• noun In architecture, same as baluster, 2.
• noun In music, the raised ridge which holds the tuning-pins of a piano.
• noun A cap-piece or short timber placed at the top of a post as a bearing for a string-piece.
• noun A perforated wooden block upon which sheet-metal is placed to be punched.
• noun A sleeve-bearing through which a spindle passes.
• noun In stone-sawing, one of the loose wooden blocks against which the ends of the pole of the saw rest.
• noun A bar placed transversely over the axle of a wagon or in the middle of a car-truck to support the body.
• noun One of the transverse pieces of an archcentering, extending between the ribs and sustaining the voussoirs during construction.

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

• transitive verb To support with a bolster or pillow.
• transitive verb To support, hold up, or maintain with difficulty or unusual effort; -- often with up.
• noun A long pillow or cushion, used to support the head of a person lying on a bed; -- generally laid under the pillows.
• noun A pad, quilt, or anything used to hinder pressure, support any part of the body, or make a bandage sit easy upon a wounded part; a compress.
• noun Anything arranged to act as a support, as in various forms of mechanism, etc.
• noun (Saddlery) A cushioned or a piece part of a saddle.
• noun A cushioned or a piece of soft wood covered with tarred canvas, placed on the trestletrees and against the mast, for the collars of the shrouds to rest on, to prevent chafing.
• noun Anything used to prevent chafing.
• noun A plate of iron or a mass of wood under the end of a bridge girder, to keep the girder from resting directly on the abutment.
• noun A transverse bar above the axle of a wagon, on which the bed or body rests.
• noun The crossbeam forming the bearing piece of the body of a railway car; the central and principal cross beam of a car truck.
• noun (Mech.) the perforated plate in a punching machine on which anything rests when being punched.
• noun That part of a knife blade which abuts upon the end of the handle.
• noun The metallic end of a pocketknife handle.
• noun (Arch.) The rolls forming the ends or sides of the Ionic capital.
• noun (Mil.) A block of wood on the carriage of a siege gun, upon which the breech of the gun rests when arranged for transportation.
• noun (Arch.) members which are bellied or curved outward like cushions, as in friezes of certain classical styles.

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

• noun A large cushion or pillow.
• noun A short, horizontal, structural timber between a post and a beam for enlarging the bearing area of the post and/or reducing the span of the beam. Sometimes also called a pillow or cross-head (Australian English).
• verb To brace, reinforce, secure, or support.

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

• verb support and strengthen
• verb prop up with a pillow or bolster
• verb add padding to
• noun a pillow that is often put across a bed underneath the regular pillows