imperfection

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

• noun The quality or condition of being imperfect.
• noun Something imperfect; a defect or flaw. synonym: blemish.

from The Century Dictionary.

• noun The character or condition of being imperfect; want of perfection; defectiveness; faultiness.
• noun An imperfect detail; a particular in which perfection is lacking; a defect, physical, mental, or moral.
• noun Synonyms Defect, deficiency, incompleteness, fault, failing, weakness, frailty, foible, blemish, vice.

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

• noun The quality or condition of being imperfect; lack of perfection; incompleteness; deficiency; fault or blemish.

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

• noun uncountable Those qualities or features that are imperfect; the characteristic, state, or quality of being imperfect.
• noun countable Something that makes something else less than perfect; a blemish, impurity, error, etc.

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

• noun the state or an instance of being imperfect