fifty-third I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 53 in a countable series < the fifty-third day > — see number table 2.: being one of 53 equal parts into which something is divisible < a fifty-third share of the money > II. noun 1.: number 53 in a countable series 2.: the quotient of a unit divided by 53 : one of 53 equal parts of something < one fifty-third of the total >