sīˈdirēəl adjective
Etymology: Latin sidere us sidereal (from sider-, sidus star, constellation + -eus -eous) + English -al; akin to Lithuanian svidus shining and probably to Old High German swīdan to burn, Old Norse svītha to burn, Old English swathul smoke
1. : of or relating to stars or constellations
sidereal system
sidereal bodies
2. : expressed in relation to the heavens above — see sidereal time