defect

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

• noun An imperfection or lack that causes inadequacy or failure; a shortcoming or deficiency. synonym: blemish.
• intransitive verb To disown allegiance to one's country and take up residence in another.
• intransitive verb To abandon a position or association, often to join an opposing group.

from The Century Dictionary.

• To be or become deficient; fail.
• To desert; revolt.
• To affect injuriously; hurt; impair; spoil.
• Defective.
• noun Want or lack of anything; especially, the lack of something which is essential to perfection or completeness; a fault; a blemish; an imperfection: as, a defect in timber; a defect in the organs of hearing or seeing; a defect of memory or judgment.
• noun Synonyms Deficiency, lack, insufficiency, failure, error, flaw.

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

• intransitive verb obsolete To fail; to become deficient.
• intransitive verb to abandon one country or faction, and join another.
• noun Want or absence of something necessary for completeness or perfection; deficiency; -- opposed to superfluity.
• noun Failing; fault; imperfection, whether physical or moral; blemish
• transitive verb rare, rare To injure; to damage.

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

• noun A fault or malfunction.
• verb intransitive To abandon or turn against; to cease or change one's loyalty.

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

• verb desert (a cause, a country or an army), often in order to join the opposing cause, country, or army
• noun an imperfection in a bodily system
• noun an imperfection in an object or machine
• noun a mark or flaw that spoils the appearance of something (especially on a person's body)
• noun a failing or deficiency