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  1. U.S. Navy. a seagoing, amphibious ship capable of carrying and launching assault landing craft from a large, inner compartment that can be flooded, and of making emergency repairs at sea to smaller ships.

Origin of LSD1

l(anding) s(hip) d(eck)


  1. Pharmacology. a crystalline solid, C20H25N3O, the diethyl amide of lysergic acid, a powerful psychedelic drug that produces temporary hallucinations and a schizophrenic psychotic state.

Origin of LSD2

From the German word Lysergsäure-Diäthylamid lysergic acid diethylamide


  1. least significant digit.


or £.s.d., l.s.d.

  1. pounds, shillings, and pence.

Origin of L.S.D.

From the Latin word librae, solidī, dēnāriī
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for lsd


  1. lysergic acid diethylamide; a crystalline compound prepared from lysergic acid, used in experimental medicine and taken illegally as a hallucinogenic drugInformal name (as an illegal hallucinogen): acid


.s.d. or l.s.d.

abbreviation for (in Britain, esp formerly)
  1. librae, solidi, denarii

Word Origin

Latin: pounds, shillings, pence
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for lsd


"lysergic acid diethylamide," 1950, from German "Lysergsäure-diäthylamid" (abbreviated LSD in a Swiss journal from 1947). See lysergic. L.s.d. as the abbreviation of "pounds, shillings, and pence" is recorded from 1853.


abbreviation of British currency units, from Latin librae, soldi, denarii, Roman equivalent of "pounds, shillings, pence."

Online Etymology Dictionary, © 2010 Douglas Harper

lsd in Medicine


  1. Lysergic acid diethylamide; a crystalline compound derived from lysergic acid and used as a powerful hallucinogenic drug.acid lysergide
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

lsd in Science


  1. Short for lysergic acid diethylamide. A crystalline compound that is a synthetic derivative of lysergic acid. It is used as a powerful hallucinogenic drug. Chemical formula: C20H25N3O.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

lsd in Culture


A drug, lysergic acid diethylamide, that produces hallucinations similar to those of a psychosis. Persons on LSD “trips,” which may last for many hours, undergo distortions of their perceptions of space and time and may lose all contact with reality.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.