valineEnglishOxford Dictionary of Englishvaline /ˈveɪliːn / ▸ noun [mass noun] Biochemistry an amino acid which is a constituent of most proteins. It is an essential nutrient in the diet of vertebrates. Chemical formula: (CH3)2CHCH(NH2)COOH. – ORIGIN early 20th century: from val(eric acid) + -ine4.