: a fatty acid C4H8O3 structurally similar to gamma-aminobutyric acid that is a depressant of the central nervous system, is used medically in the form of its sodium salt C4H7NaO3 especially to treat narcolepsy, is used illicitly in the form of one of several salts to produce sedative and euphoric effects, and is sometimes abused by athletes and body builders to stimulate the release of growth hormone although it has not been shown to increase muscle mass