acid - any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt

atomic number 16, sulfur, sulphur, S - an abundant tasteless odorless multivalent nonmetallic element; best known in yellow crystals; occurs in many sulphide and sulphate minerals and even in native form (especially in volcanic regions)

battery acid, electrolyte acid - dilute sulfuric acid used in storage batteries