Entry 4 senses · 2 variants Webster, 1913 Sixtieth /sĭk'-stē-ĭth/ · Six·ti·eth · IPA /ˈsɪksti.əθ/ a. n. 01 a. Next in order after the fifty-ninth. 1. Next in order after the fifty-ninth. 2. Constituting or being one one of sixty equal parts into which anything is divided. 02 n. The quotient of a unit divided by sixty; one of sixty equal parts forming a whole. 1. The quotient of a unit divided by sixty; one of sixty equal parts forming a whole. 2. The next in order after the fifty-ninth; the tenth after the fiftieth.