What is Bolster?

Bolster definition and meaning on Dictionary terms:
a long, often cylindrical, cushion or pillow for a bed, sofa, etc.
anything resembling this in form or in use as a support.
any pillow, cushion, or pad.
Nautical. Also called bolster plate.a circular casting on the side of a vessel, through which an anchor chain passes.a timber used as a temporary support.a beam for holding lines or rigging without chafing.a bag filled with buoyant material, fitted into a small boat.

Metalworking. an anvillike support for the lower die of a drop forge.
Masonry. a timber or the like connecting two ribs of a centering.a chisel with a blade splayed toward the edge, used for cutting bricks.

Carpentry. a horizontal timber on a post for lessening the free span of a beam.
a structural member on which one end of a bridge truss rests.

verb (used with object)
to support with or as with a pillow or cushion.
to add to, support, or uphold (sometimes followed by up): They bolstered their morale by singing. He bolstered up his claim with new evidence.