metastasis

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

• noun Transmission of pathogenic microorganisms or cancerous cells from an original site to one or more sites elsewhere in the body, usually by way of the blood vessels or lymphatics.
• noun A secondary cancerous growth formed by transmission of cancerous cells from a primary growth located elsewhere in the body.

from The Century Dictionary.

• noun In petrography, a change within a rock or mineral in the nature of recrystallization or molecular rearrangement, without the addition or subtraction of material: as the crystallization of a limestone, or the devitrification of glass.
• noun Change of substance; conversion of one substance into another.
• noun In pathology, the production of local disease in some part of the body from a focus of more or less similar disease in some other part not immediately adjacent.
• noun In botany, metabolism.

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

• noun (Theol.) A spiritual change, as during baptism.
• noun (Med.) A change in the location of a disease, as from one part to another.
• noun The migration of cancerous or malignant cells from the site of their origin to other parts of the body. Such cells may migrate to multiple new locations, making therapy more difficult and often leading to death.
• noun (Physiol.) The act or process by which matter is taken up by cells or tissues and is transformed into other matter; in plants, the act or process by which are produced all of those chemical changes in the constituents of the plant which are not accompanied by a production of organic matter; metabolism.

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

• noun medicine The transference of a bodily function or disease to another part of the body, specifically the development of a secondary area of disease remote from the original site, as with some cancers.
• noun rhetoric Denying adversaries' arguments and turning the arguments back on them.

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

• noun the spreading of a disease (especially cancer) to another part of the body