Definition of LSD
: a semisynthetic illicit organic compound C20H25N3O derived from ergot that induces extreme sensory distortions, altered perceptions of reality, and intense emotional states, that may also produce delusions or paranoia, and that may sometimes cause panic reactions in response to the effects experienced
— called also lysergic acid diethylamide
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Merriam-Webster unabridged
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The first known use of LSD was in 1950
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