drop cloth

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

• noun A sheet, as of cloth or plastic, for protection against spills or dripping, used especially by painters.

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

• noun a sheet of material used to cover objects or surfaces while painting a ceiling or wall of a house, so as to protect objects from being marred by drops of paint splashed inadvertantly in the painting process. Originally such drop cloths were made of cloth, but more recently paper or plastic have also commonly been used.

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

• noun An impermeable sheet of material meant to catch paint or other hard-to-clean substances.

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

• noun a large piece of cloth laid over the floor or furniture while a room is being painted
• noun a curtain that can be lowered and raised onto a stage from the flies; often used as background scenery