This definition refers to the definition of measurand provided by the 3rd edition of the International Vocabulary of Metrology provided by the JCGM. 

Note 1 of the JCGM definition provides details on the scope and meaning of a measurand: "The specification of a measurand requires knowledge of the kind of quantity, description of the state of the phenomenon, body, or substance carrying the quantity, including any relevant component, and the chemical entities involved."