Also found in: Dictionary, Wikipedia.
Related to diurnal motion: sidereal day
diurnal motionThe apparent daily motion of celestial bodies across the sky from east to west. It results from the Earth's rotation from west to east, the axis of the diurnal motion coinciding with the Earth's axis. The apparent path of a celestial body arising from diurnal motion is a circle parallel to the celestial equator and is termed a diurnal circle.
diurnal motion[dī′ərn·əl ′mō·shən]
The apparent daily motion of a celestial body as observed from a rotating body.