Ninetieth

1. n. The next in order after the eighty-ninth.
2. a. Next in order after the eighty-ninth.
3. a. Constituting or being one of ninety equal parts.
4. n. The quotient of a unit divided by ninety; one of ninety equal parts of anything.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.