infection

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

• noun The invasion of bodily tissue by pathogenic microorganisms that proliferate, resulting in tissue injury that can progress to disease.
• noun The entry or placement, as by injection, of a microorganism or infectious agent into a cell or tissue.
• noun An instance of being infected.
• noun An agent or a contaminated substance responsible for one's becoming infected.
• noun The pathological state resulting from having been infected.
• noun An infectious disease.
• noun An instance of a virus or similar software program infecting a computer.
• noun The communication of a usually undesirable idea, emotion, or attitude by contact with other people or by example.

from The Century Dictionary.

• noun In biology, the hypothetical influence upon the tissues of the mother animal by the sperm of a male, such that subsequent offspring of the mother by other sires are infected with the characteristics of the first sire: a hypothesis invented to account for telegony. See telegony.
• noun The act of infecting.
• noun The communication of disease or of disease-germs, whether by contact with a diseased person or with morbid or noxious matter, contaminated clothing, etc., or by poisonous exhalations from any source. Compare contagion, 1.
• noun Contamination by illegality, as in possessing contraband goods, etc.
• noun That which infects, or by which some quality or state is communicated.
• noun That which taints, poisons, or corrupts by communication from one to another; contaminating influence: as, the infection of error, or of an evil example.
• noun That by which disease is or may be communicated; an infecting agency; morbific emanation or influence; virus.
• noun In grammar, a modification of a vowel-sound by another following, whereby the first takes on the sound of the second: applied to such modification in Celtic speech. Windisch, Irish Gram. (trans.).

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

• noun The act or process of infecting.
• noun That which infects, or causes the communicated disease; any effluvium, miasm, or pestilential matter by which an infectious disease is caused.
• noun The state of being infected; the condition of suffering from an infectious disease; contamination by morbific particles; the result of infecting influence; a prevailing disease; epidemic.
• noun That which taints or corrupts morally.
• noun (Law) Contamination by illegality, as in cases of contraband goods; implication.
• noun Sympathetic communication of like qualities or emotions; influence.
• noun A localized area of tissue which is inflamed by growth of microorganisms.

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

• noun pathology The act or process of infecting.
• noun An uncontrolled growth of harmful microorganisms in a host.

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

• noun an incident in which an infectious disease is transmitted
• noun the pathological state resulting from the invasion of the body by pathogenic microorganisms
• noun the communication of an attitude or emotional state among a number of people
• noun moral corruption or contamination
• noun (international law) illegality that taints or contaminates a ship or cargo rendering it liable to seizure
• noun (medicine) the invasion of the body by pathogenic microorganisms and their multiplication which can lead to tissue damage and disease
• noun (phonetics) the alteration of a speech sound under the influence of a neighboring sound