(organic chemistry, especially in combination) Either the univalent or the divalent radicals derived from oxalic acid by removal of one or two hydrogen atoms

(organic chemistry) An organic compound with the chemical formula (COCl)₂, the diacid chloride of oxalic acid, a useful reagent in organic synthesis.

(organic chemistry) An amide formed from condensation of oxalic acid and the amino group of glycine; it is an inhibitor of some classes of enzymes