casing

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

• noun An outer cover.
• noun The frame or framework for a window or door.
• noun A metal pipe or tube used as a lining for a water, oil, or gas well.
• noun A membranous case, often made of animal intestine, used to contain sausage or other processed meat.
• noun A narrow passage for a rod or cord, as in a curtain or the waistband of a garment, made by folding over a small strip of fabric at its edge along its width and sewing it in place.

from The Century Dictionary.

• noun The act or process expressed by the verb case.
• noun A case; a covering; an inclosure.
• noun The process of putting tobacco leaf into the desired ‘case’ or condition, namely by moistening, and adding the ingredients used to give flavor, etc. See case, n., 9.

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

• noun The act or process of inclosing in, or covering with, a case or thin substance, as plaster, boards, etc.
• noun An outside covering, for protection or ornament, or to precent the radiation of heat.
• noun An inclosing frame; esp. the framework around a door or a window. See Case, n., 4.

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

• noun That which encloses or encases.
• noun uncountable, computing The collective states of upper and lower case letters.
• verb Present participle of case.

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

• noun the housing or outer covering of something
• noun the outermost covering of a pneumatic tire
• noun the enclosing frame around a door or window opening