sixty-fourth I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 64 in a countable series < the sixty-fourth day > — see number table 2.: being one of 64 equal parts into which something is divisible < a sixty-fourth share of the money > II. noun 1.: number 64 in a countable series 2.: the quotient of a unit divided by 64 : one of 64 equal parts of something < one sixty-fourth of the total >