Webster’s Revised Unabridged Dictionary · 1913
Eightieth
Eight′i·eth (ā′tĭ·ĕth), a. [From Eighty.] 1. The next in order after seventy-ninth.
2. Consisting of one of eighty equal parts or divisions.
Eight′i·eth, n. The quotient of a unit divided by eighty; one of eighty equal parts.