(Science: chemistry) Of or pertaining to tartar; derived from, or resembling, tartar. Tartaric acid. An acid widely diffused throughout the vegetable kingdom, as in grapes, mountain-ash berries, etc, and obtained from tartar as a white crystalline substance, C2H2(OH)2.(CO2H)2, having a strong pure acid taste. It is used in medicine, in dyeing, calico printing, photography, etc, and also as a substitute for lemon juice. Called also dextro-tartaric acid. By extension, any one of the series of isomeric acids (racemic acid, levotartaric acid, inactive tartaric acid) of which tartaric acid proper is the type.