statistical term for survival data that is the duration cut off at a specified time: here either the date of death or date of last information or follow-up.
See ref below for complete explanation of "censored" in this context.
From that:
"In many medical studies an outcome of interest is the time to an event. Such events may be adverse, such as death or recurrence of a tumour; positive, such as conception or discharge from hospital; or neutral, such as cessation of breast feeding. It is conventional to talk about survival data and survival analysis, regardless of the nature of the event. Similar data also arise when measuring the time to complete a task, such as walking 50 metres.

The distinguishing feature of survival data is that at the end of the follow up period the event will probably not have occurred for all patients. For these patients the survival time is said to be censored, indicating that the observation period was cut off before the event occurred. We do not know when (or, indeed, whether) the patient will experience the event, only that he or she has not done so by the end of the observation period.

Censoring may also occur in other ways. Patients may be lost to follow up during the study, or they may experience a "competing" event which makes further follow up impossible. For example, patients being followed to a cardiac event may die from some other disease or in an accident."

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Note added at 2 jours5 heures (2008-01-10 15:16:04 GMT)
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book title available on amazon.com: Survival Analysis: Techniques for Censored and Truncated Data (Statistics for Biology and Health) (Hardcover)
by John P. Klein (Author), Melvin L. Moeschberger (Author)
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Biometrics. 1992 Jun;48(2):411-25.Links
Relative risk trees for censored survival data.

LeBlanc M, Crowley J.
Department of Preventive Medicine and Biostatistics, University of Toronto, Canada.
A method is developed for obtaining tree-structured relative risk estimates for censored survival data. The first step of a full likelihood estimation procedure is used in a recursive partitioning algorithm that adopts most aspects of the widely used Classification and Regression Tree (CART) algorithm of Breiman et al. (1984, Classification and Regression Trees, Belmont, California: Wadsworth). The performance of the technique is investigated through stimulation and compared to the tree-structured survival methods proposed by Davis and Anderson (1989, Statistics in Medicine 8, 947-961) and Therneau, Grambsch, and Fleming (1990, Biometrika 77, 147-160).


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Note added at 2 jours5 heures (2008-01-10 15:17:01 GMT)
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reference quoted from above "in many medical studies...." is from
http://www.bmj.com/cgi/content/full/317/7156/468