Definition of light year noun from the Oxford Advanced Learner's Dictionary

     

    light year

     noun
    noun
    BrE
     
    ; NAmE
     
    The universe
     
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  1. 1(astronomy) the distance that light travels in one year, 9.4607 × 1012 kilometres The nearest star to earth is about 4 light years away. See related entries: The universe
  2. 2light years [plural] a very long time Full employment still seems light years away.
See the Oxford Advanced American Dictionary entry: light year