[som-nam-byuh-liz-uhm, suhm-]

1790–1800; < Neo-Latin somnambulismus, equivalent to somn(us) sleep + ambul(āre) to walk + -ismus -ism

somnambulist, noun
somnambulistic, adjective
semisomnambulistic, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
somnambulism (sɒmˈnæmbjʊˌlɪzəm)
Also called: noctambulism a condition that is characterized by walking while asleep or in a hypnotic trance

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

1794 (as somnambulation), from Mod.L. somnambulus "sleepwalker," from L. somnus "sleep" (see somnolence) + ambulare "to walk" (see amble). Won out over noctambulation. To talk in one's sleep is somniloquence (1841).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

somnambulism som·nam·bu·lism (sŏm-nām'byə-lĭz'əm)
See sleepwalking.

som·nam'bu·lis'tic adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia Britannica


a behavioral disorder of sleep in which a person sits up and performs various motor actions, such as standing, walking about, talking, eating, screaming, dressing, going to the bathroom, or even leaving the house. The episode usually ends with the sleepwalker returning to sleep, with no subsequent memory of the episode. Sleepwalking is most common in children, though it may also appear in adolescents and young adults. It occurs only during deep sleep, when dreams are basically absent. Sleepwalking becomes dangerous only when the possibility exists of the sleepwalker accidentally injuring himself.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Describes therapy program for treating somnambulism.
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