Security Glossary - L

This glossary has been created to assist security professionals in defining security terms commonly used by the profession and the industry, worldwide. It is a developing list that will be maintained, and where appropriate, modified, and changed over time. Terms borrowed from related fields, such as engineering, investigations, safety, etc. will be included when deemed necessary for the security professional.


The definition's source is cited in brackets [ ] following the definition. View the key to all cited reference sources.

It is NOT our goal to publish this glossary in print since it is intended to be a current online reference (on the ASIS website) to serve the security professional on an ongoing basis.

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less-lethal weapons

​Weapons, devices, and munitions that continue to pose a great risk of lethal injury but the intent is not to cause death or bodily harm and do not measure up to the definition of “likely” in a court environment.
[ANSI/ASIS PSC.4-2013]


​A legal right or interest that a creditor has in another’s property, lasting usually until a debt or duty that it secures is satisfied.


​A degree of illumination; also, equipment, used indoors and outdoors, for increasing illumination (usually measured in lux or foot-candle units).   
[ASIS GDL FPSM-2009]  [ANSI/ASIS PAP.1-2012]


(1) ​Chance of something happening.
Note 1: In risk management terminology the word “likelihood” is used to refer to the chance of something happening, whether defined, measured or determined objectively or subjectively, qualitatively or quantitatively, and described using general terms or mathematically (such as a probability or a frequency over a given time period).
[ANSI/ASIS PSC.1-2012]
Note 2: The English term likelihood does not have a direct equivalent in some languages; instead, the equivalent of the term probability is often used. However, in English, probability is often narrowly interpreted as a mathematical term. Therefore, in risk management terminology, likelihood is used with the intent that it should have the same broad interpretation as the term probability has in many languages other than English.
[ANSI/ASIS PAP.1-2012] [ANSI/ASIS SCRM.1-2014]

(2) Chance or probability of something happening.


​A piece of equipment used to prevent undesired opening, typically of an aperture (gate, window, building door, vault door, etc.), while still allowing opening by authorized users.
[ASIS GDL FPSM-2009]  [ANSI/ASIS PAP.1-2012]

look-back (inwards) surveillence

​A method of surveillance that concentrates on reviewing and evaluating individuals and equipment that is focused on monitoring one’s activities.
[ASIS GDL TASR 04 2008]

loss event

​An occurrence that produces a financial loss or negative impact on assets. Examples include security incidents, crimes, war, natural hazards, or disasters.
[ASIS GDL GLCO 01 012003]