Bible Dictionaries
Semidiurnal

Webster's Dictionary

(1):

(a.) Pertaining to, or accomplished in, half a day, or twelve hours; occurring twice every day.

(2):

(a.) Pertaining to, or traversed in, six hours, or in half the time between the rising and setting of a heavenly body; as, a semidiurnal arc.

Bibliography Information
Webster, Noah. Entry for 'Semidiurnal'. Noah Webster's American Dictionary. https://www.studylight.org/​dictionaries/​eng/​web/​s/semidiurnal.html. 1828.