Definition of light-year
1
: a unit of length in astronomy equal to the distance that light travels in one year in a vacuum or about 5.88 trillion miles (9.46 trillion kilometers)
2
: an extremely large measure of comparison (as of distance, time, or quality)
seems like light-years ago has light-years more talent two minutes and yet light-years away from the crowded village— Suzanne Patterson
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Merriam-Webster unabridged
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Time Traveler for light-year
The first known use of light-year was in 1867
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