ninety-ninth I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 99 in a countable series < the ninety-ninth day > — see number table 2.: being one of 99 equal parts into which something is divisible < a ninety-ninth share of the money > II. noun 1.: number 99 in a countable series 2.: the quotient of a unit divided by 99 : one of 99 equal parts of something