gamma-aminobutyric acid: a biologically active substance found in plants and in brain and other animal tissues; it is a neurotransmitter that inhibits activation of neurones
GABA in American English
(ˈgæbə; ˈgɑbə; ˈgɑˌbɑ)
noun
an amino acid, H2N(CH2)3COOH, found in plants and in nervous tissue, esp. in the brain, where it acts as a neurotransmitter that suppresses nerve activity