Real Dictionary

plaster
uncountable noun: Plaster is a smooth paste made of sand, lime, and water which goes hard when it dries. Plaster is used to cover walls and ceilings and is also used to make sculptures.
verb: If you plaster a wall or ceiling, you cover it with a layer of plaster.

plaster in American English
a pasty mixture, as of lime or gypsum, sand, and water, which hardens on drying, for coating walls, ceilings, and partitions
to cover, smear, overlay, etc. with or as with plaster
noun: a composition, as of lime or gypsum, sand, water, and sometimes hair or other fiber, applied in a pasty form to walls, ceilings, etc., and allowed to harden and dry
transitive verb: to cover (walls, ceilings, etc.) with plaster

plaster in British English
noun: a mixture of lime, sand, and water, sometimes stiffened with hair or other fibres, that is applied to the surface of a wall or ceiling as a soft paste that hardens when dry