Ester \Es"ter\, n. [A word invented by L. Gmelin, a German chemist.]

(Chem.) An ethereal salt, or compound ether, consisting of an organic radical united with the residue of any oxygen acid, organic or inorganic; thus the natural fats are esters of glycerin and the fatty acids, oleic, etc.

Source: Webster's Revised Unabridged Dictionary (1913)