Thir"teenth` (?), a. [From Thirteen: cf. AS. þreóteóða.] 1. Next in
order after the twelfth; the third after the tenth; — the ordinal of
thirteen; as, the thirteenth day of the month.
2. Constituting or being one of thirteen equal parts into which
anything is divided.
Thir"teenth`, n. 1. The quotient of a unit divided by thirteen; one of
thirteen equal parts into which anything is divided.