Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic

Semisynthetic

"Semisynthesis" or partial chemical synthesis is a type of chemical synthesis that uses compounds isolated from natural sources as starting materials. These natural biomolecules are usually large and complex molecules...

 psychedelic drug

Psychedelic drug

A psychedelic substance is a psychoactive drug whose primary action is to alter cognition and perception. Psychedelics are part of a wider class of psychoactive drugs known as hallucinogens, a class that also includes related substances such as dissociatives and deliriants...

 of the ergoline

Ergoline

Ergoline is a chemical compound whose structural skeleton is contained in a diverse range of alkaloids including a few psychedelic drugs . Ergoline derivatives are used clinically for the purpose of vasoconstriction and in the treatment of migraines and Parkinson's disease...

 family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an altered sense of time

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 and spiritual experiences

Religious experience

Religious experience is a subjective experience in which an individual reports contact with a transcendent reality, an encounter or union with the divine....

, as well as for its key role in 1960s counterculture

Counterculture of the 1960s

The counterculture of the 1960s refers to a cultural movement that mainly developed in the United States and spread throughout much of the western world between 1960 and 1973. The movement gained momentum during the U.S. government's extensive military intervention in Vietnam...

. It is used mainly as an entheogen

Entheogen

An entheogen , in the strict sense, is a psychoactive substance used in a religious, shamanic, or spiritual context. Historically, entheogens were mostly derived from plant sources and have been used in a variety of traditional religious contexts...

, recreational drug

Recreational drug use

Recreational drug use is the use of a drug, usually psychoactive, with the intention of creating or enhancing recreational experience. Such use is controversial, however, often being considered to be also drug abuse, and it is often illegal...

, and as an agent in psychedelic therapy.