forty-fifth I. \| ̷ ̷ ̷ ̷| ̷ ̷\adjective 1.: being number 45 in a countable series < the forty-fifth day > — see number table 2.: being one of 45 equal parts into which something is divisible < a forty-fifth share of the money > II. noun 1.: number 45 in a countable series 2.: the quotient of a unit divided by 45 : one of 45 equal parts of something < one forty-fifth of the total >