A type of cell death in which the cell uses specialized cellular machinery to kill itself; a cell suicide mechanism that enables metazoans to control cell number and eliminate cells that threaten the animal's survival programmed cell death, caspase-mediated cell death]
WordNet® 2.0© 2003 Princeton University
A More Technical Definition
Programmed cell death, or "cell suicide"; a form of cell death in which a controlled sequence of events (or program) leads to the elimination of cells without releasing harmful substances into the surrounding area. Many types of cell damage can trigger apoptosis, and it also occurs normally during development of the nervous system and other parts of the body. Strictly speaking, the term apoptosis refers only to the structural changes cells go through, and programmed cell death refers to the complete underlying process, but the terms are often used synonymously.
National Institute of Neurological Disorders and Stroke. 2005. Spinal Cord Injuries: Emerging Concepts. Available at: http://www.ninds.nih.gov/news_and_events/proceedings/sci_report.htm
A visual image of the process of apoptosis can be found at the Genetics Home Reference, a Service of the U.S. National Library of Medicine®
The process of apoptosis. Genetics Home Reference. U.S. National Library of Medicine® http://ghr.nlm.nih.gov/handbook/illustrations/apoptosisprocess