tyrosinePronunciation: /ˈtʌɪrəsiːn/Definition of tyrosine noun [mass noun] Biochemistry a hydrophilic amino acid which is a constituent of most proteins and is important in the synthesis of some hormones. Chemical formula: C6H4(OH)CH2CH(NH2)COOH Origin: mid 19th century: formed irregularly from Greek turos 'cheese' + -ine4tyrosine in other Oxford dictionaries Definition of tyrosine in the US English dictionary