fifty-eighth I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 58 in a countable series < the fifty-eighth day > — see number table 2.: being one of 58 equal parts into which something is divisible < a fifty-eighth share of the money > II. noun 1.: number 58 in a countable series 2.: the quotient of a unit divided by 58 : one of 58 equal parts of something < one fifty-eighth of the total >