discoloration

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

• noun The act of discoloring.
• noun The condition of being discolored.
• noun A discolored spot, smudge, or area; a stain.

from The Century Dictionary.

• noun The act of discoloring, or the state of being discolored; alteration of color.
• noun That which is discolored; a discolored spot; a stain: as, spots and discolorations of the skin.
• noun Specifically In entomology, an indistinct, paler, or discolored part of a surface; that which is colorless or nearly so, as if faded out.
• noun Alteration of complexion or of the appearance of things: as, the discoloration of ideas.

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

• noun The act of discoloring, or the state of being discolored; alteration of hue or appearance.
• noun A discolored spot; a stain.

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

• noun The act of discoloring, or the state of being discolored; alteration of hue or appearance.
• noun A discolored spot; a stain.

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

• noun the act of changing the natural color of something by making it duller or dingier or unnatural or faded
• noun a soiled or discolored appearance