LSD is an acronym for lysergic ACID diethylamide, a powerful hallucinogenic drug. It was first synthesized in 1938 by Swiss chemist Albert Hofmann and was used in psychiatric research until it was made illegal in the late 1960s. LSD is known for its ability to produce vivid hallucinations and altered states of consciousness. It is also associated with the counterculture movement of the 1960s and 1970s.