( 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.
( 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.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012