sixty-third I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 63 in a countable series < the sixty-third day > — see number table 2.: being one of 63 equal parts into which something is divisible < a sixty-third share of the money > II. noun 1.: number 63 in a countable series 2.: the quotient of a unit divided by 63 : one of 63 equal parts of something < one sixty-third of the total >