OXALIC ACID Meaning of OXALIC ACID in English n. Chem. a very poisonous and sour acid found in sorrel and rhubarb leaves. Usage: Chem. formula: (COOH)2 Derivatives: oxalate n. Etymology: F oxalique f. L oxalis f. Gk oxalis wood sorrel Oxford English vocab. Оксфордский английский словарь. 2012