Definition of sidereal adjective from the Oxford Advanced Learner's Dictionary

 

sidereal

 adjective
adjective
BrE BrE//saɪˈdɪəriəl//
 
; NAmE NAmE//saɪˈdɪriəl//
 
(astronomy)
 
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related to the stars that are far away, not the sun or planets Word Origin mid 17th cent.: from Latin sidereus (from sidus, sider- ‘star’) + -al.
See the Oxford Advanced American Dictionary entry: sidereal