gamma-aminobutyric acid \¦gamə.ə¦mē(ˌ)nō, -mə¦amə̇(ˌ)nōˌ…-\noun alsoγ-aminobutyric acid\"\ Etymology:gamma (II) + amin- + butyric acid : an amino acid C4H9NO2 that is a neurotransmitter that induces inhibition of postsynaptic neurons — abbreviation GABA