Origin:
L acidus, sour < IE base *a-, sharp, pointed > ear
noun
a sour substance
Slang LSD
Chem. any compound that can react with a base to form a salt, the hydrogen of the acid being replaced by a positive ion; in modern theory, any substance that produces a positive ion and accepts electrons from a base to form covalent bonds: in water solution an acid tastes sour, turns blue litmus paper red, and, in the dissociation theory, produces free hydrogen ions