dissociation

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

• noun The act of dissociating or the condition of having been dissociated.
• noun The process by which the action of a solvent or a change in physical condition, as in pressure or temperature, causes a molecule to split into simpler groups of atoms, single atoms, or ions.
• noun The separation of an electrolyte into ions of opposite charge.
• noun Psychiatry A psychological defense mechanism in which specific, anxiety-provoking thoughts, emotions, or physical sensations are separated from the rest of the psyche.

from The Century Dictionary.

• noun In psychology: The disjunction of an associative connection, as by lapse of memory or by intercurrent associations, by the selective process of active attention, etc.
• noun A minor degree of the disintegration or disaggregation of consciousness, as it is termed, which culminates in the phenomena of dual or multiple personality.
• noun The severance of association or connection; separation; disunion.
• noun Specifically In chem., the resolution of more complex into simpler molecules by the action of heat. Also called thermolysis.

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

• noun The act of dissociating or disuniting; a state of separation; disunion.
• noun (Chem.) The process by which a compound body breaks up into simpler constituents; -- said particularly of the action of heat on gaseous or volatile substances

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

• noun The act of dissociating or disuniting; a state of separation; disunion.
• noun chemistry The process by which a compound body breaks up into simpler constituents; said particularly of the action of heat on gaseous or volatile substances.
• noun psychology A defence mechanism where certain thoughts or mental processes are compartmentalised in order to avoid emotional stress to the conscious mind.

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

• noun a state in which some integrated part of a person's life becomes separated from the rest of the personality and functions independently
• noun the act of removing from association
• noun (chemistry) the temporary or reversible process in which a molecule or ion is broken down into smaller molecules or ions